5100.2-2017-design loads
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AS 5100.2:2017
Accessed by CENTRAL QUEENSLAND UNIVERSITY on 06 Jun 2017 (Document currency not guaranteed when printed)
AP-G51.2-17
AS 5100.2:2017
Bridge design
Part 2: Design loads
This Australian Standard® was prepared by Committee BD-090, Bridge Design. It was approved on behalf of the Council of Standards Australia on 13 March 2017. This Standard was published on 31 March 2017.
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The following are represented on Committee BD-090:
Australian Industry Group Australian Steel Institute Austroads Bureau of Steel Manufacturers of Australia Cement and Concrete Association of New Zealand Cement Concrete & Aggregates Australia—Cement Concrete Institute of Australia Consult Australia Engineers Australia New Zealand Heavy Engineering Research Association Rail Industry Safety and Standards Board Steel Construction New Zealand Steel Reinforcement Institute of Australia Sydney Trains
This Standard was issued in draft form for comment as DR AS 5100.2:2016. Standards Australia wishes to acknowledge the participation of the expert individuals that contributed to the development of this Standard through their representation on the Committee and through the public comment period.
Keeping Standards up-to-date Australian Standards® are living documents that reflect progress in science, technology and systems. To maintain their currency, all Standards are periodically reviewed, and new editions are published. Between editions, amendments may be issued. Standards may also be withdrawn. It is important that readers assure themselves they are using a current Standard, which should include any amendments that may have been published since the Standard was published. Detailed information about Australian Standards, drafts, amendments and new projects can be found by visiting www.standards.org.au Standards Australia welcomes suggestions for improvements, and encourages readers to notify us immediately of any apparent inaccuracies or ambiguities. Contact us via email at [email protected], or write to Standards Australia, GPO Box 476, Sydney, NSW 2001.
AS 5100.2:2017
Australian Standard®
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Bridge design Part 2: Design loads
First published as HB 77.2—1996. Revised and redesignated as AS 5100.2—2004. Second edition 2017.
COPYRIGHT © Standards Australia Limited All rights are reserved. No part of this work may be reproduced or copied in any form or by any means, electronic or mechanical, including photocopying, without the written permission of the publisher, unless otherwise permitted under the Copyright Act 1968. Published by SAI Global Limited under licence from Standards Australia Limited, GPO Box 476, Sydney, NSW 2001, Australia ISBN 978 1 76035 715 3
AS 5100.2:2017
2
PREFACE This Standard was prepared by the Standards Australia Committee BD-090, Bridge Design, to supersede AS 5100.2—2004. This Standard is also designated as Austroads publication AP-G51.2-17. The objectives of the AS(AS/NZS) 5100 series are to provide nationally acceptable requirements for— (a)
the design of road, rail, pedestrian and cyclist path bridges;
(b)
the specific application of concrete, steel, timber and composite construction, which embody principles that may be applied to other materials in association with relevant standards;
(c)
the assessment of the load capacity of existing bridges; and
(d)
the strengthening and rehabilitation of existing bridges.
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The objective of this Part (AS 5100.2) is to specify minimum design loads and load effects for road, rail, pedestrian and cyclist path bridges, and other associated structures. The requirements of the AS(AS/NZS) 5100 series are based on the principles of structural mechanics and knowledge of material properties, for both the conceptual and detailed design, to achieve acceptable probabilities that the bridge or associated structure being designed will not become unfit for use during its design life. Significant differences between this Standard and AS 5100.2—2004 are the following: (i)
Changes and clarifications to the provision for collision loads from rail traffic.
(ii)
Changes to dynamic load allowance for rail traffic load effects.
(iii) Addition to provisions for bridge collision from waterway traffic. (iv)
Updated bridge traffic barrier loads to more closely reflect vehicles currently using the road network. Barrier test levels and minimum effect heights were adopted from the AASHTO Manual for Assessing Safety Hardware (MASH 2009) which replaced NCHRP Report 350 (1993).
(v)
Earthquake design procedures for bridges rewritten to align with the current earthquake loading Standard AS 1170.4—2007, Structural design actions, Part 4: Earthquake actions in Australia. New displacement-based earthquake design procedures were included.
(vi)
Improvement to serviceability and fatigue limit states for road signs and lighting structures.
(vii) Expansion of water flow forces to include impact from large moving objects during flood events. (viii) Addition of light rail vehicles. Other differences between this Standard and AS 5100.2—2004 are the following: (A)
Improved pedestrian and cyclist path barrier loads.
(B)
Expanded dynamic loads for pedestrian and cyclist path bridges.
(C)
New table for unfactored vertical pressure due to design rail traffic loads.
(D)
Inclusion of super-t girders in the calculation of bridge thermal effects.
(E)
Clarification of loads and load factors for construction loads.
(F)
Addition of protective screen design for wind load and robustness.
3
(G)
AS 5100.2:2017
New fire effect load case.
A number of new or revised appendices have been added to this edition of the Standard, which provide additional information and guidance as follows: (1)
Update to special performance level bridge barrier loads.
(2)
New alternative force-based earthquake design procedures.
(3)
Bending moment and shear force for SM1600 and 300LA loads for simply supported spans.
(4)
A summary of load factors and load combinations.
In line with Standards Australia editorial policy, the words ‘shall’ and ‘may’ are used consistently throughout this Standard to indicate, respectively, a mandatory provision and an acceptable or permissible alternative. Statements expressed in mandatory terms in Notes to Tables are deemed to be requirements of this Standard.
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The term ‘informative’ has been used in this Standard to define the application of the appendix to which it applies. An ‘informative’ appendix is only for information and guidance.
AS 5100.2:2017
4
CONTENTS
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Page 1
SCOPE AND GENERAL ............................................................................................ 5
2
NORMATIVE REFERENCES .................................................................................... 6
3
DEFINITIONS............................................................................................................. 6
4
NOTATION ................................................................................................................. 7
5
MATTERS FOR RESOLUTION BEFORE DESIGN COMMENCES ...................... 13
6
DEAD LOADS (G) .................................................................................................... 14
7
ROAD TRAFFIC (Q) ................................................................................................ 18
8
PEDESTRIAN, CYCLIST PATH AND MAINTENANCE TRAFFIC (Q) ................ 29
9
RAIL TRAFFIC (Q) .................................................................................................. 31
10
MINIMUM RESTRAINT LOAD .............................................................................. 42
11
COLLISION LOADS ................................................................................................ 42
12
KERB AND BARRIER DESIGN LOADS AND OTHER REQUIREMENTS FOR ROAD TRAFFIC BRIDGES ..................................................................................... 47
13
DYNAMIC BEHAVIOUR ........................................................................................ 51
14
EARTH PRESSURE FROM TRAFFIC LOADS ....................................................... 54
15
EARTHQUAKE EFFECTS ....................................................................................... 58
16
FORCES RESULTING FROM WATER FLOW ....................................................... 67
17
WIND LOADS .......................................................................................................... 76
18
THERMAL EFFECTS ............................................................................................... 79
19
SHRINKAGE, CREEP AND PRESTRESS EFFECTS .............................................. 84
20
DIFFERENTIAL MOVEMENT OF SUPPORTS ...................................................... 84
21
FORCES FROM BEARINGS .................................................................................... 85
22
CONSTRUCTION FORCES AND EFFECTS ........................................................... 85
23
LOAD COMBINATIONS ......................................................................................... 88
24
ROAD SIGNS AND LIGHTING STRUCTURES ..................................................... 90
25
NOISE BARRIERS AND PROTECTION SCREENS ............................................... 92
26
FIRE EFFECTS ......................................................................................................... 93
APPENDICES A DESIGN LOADS FOR SPECIAL PERFORMANCE LEVEL BARRIERS............... 95 B DISPLACEMENT-BASED EARTHQUAKE DESIGN............................................. 96 C SM1600 AND 300LA LOAD EFFECTS FOR SIMPLY SUPPORTED SPANS ..... 118 D SUMMARY OF LOAD FACTORS AND COMBINATIONS................................. 121 BIBLIOGRAPHY ................................................................................................................... 130
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AS 5100.2:2017
STANDARDS AUSTRALIA Australian Standard Bridge design Part 2: Design loads 1 SCOPE AND GENERAL 1.1 Scope This Standard sets out minimum design loads, forces and load effects for road, rail, pedestrian and cyclist path bridges, and other associated structures. 1.2 General Structures shall be proportioned for the design loads, forces and load effects in accordance with Clauses 6 to 26, as appropriate.
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NOTE: If the relevant authority approves, the designer may vary any of the loads set out in this Standard, provided the provisions of AS 5100.1 are complied with.
The design loads and forces shall be considered as acting in combinations as set out in Clause 23. NOTE: A summary of load factors is tabulated in Appendix D.
Each individual bridge shall be assessed to ascertain whether any other loads, forces or load effects are applicable for that particular design. The magnitude of these additional forces or load effects and their combination with other loads shall be consistent with the principles set out in AS 5100.1. On the front sheet of the bridge drawings, the following details relating to design loads shall be shown, where relevant: (a)
The Standard used.
(b)
Any significant variation to the minimum design loads as set out in this Standard.
(c)
Traffic load, e.g. 300LA and SM1600, including lateral position, if critical, and the number of design lanes.
(d)
Design traffic speed.
(e)
Fatigue criteria, including number of cycles and route factor.
(f)
Pedestrian loads, both horizontal and vertical.
(g)
Collision load on the structure (e.g. substructure and superstructure where applicable) or alternative load paths provided.
(h)
Design wind speeds.
(i)
Flood data, e.g. design velocities, levels, debris, and the like.
(j)
Earthquake criteria.
(k)
Differential settlements and mining subsidence effects allowed for in the design.
(l)
Foundation data where not shown elsewhere.
(m)
Barrier performance level.
(n)
The construction loads, methods and sequence, and any other specific limitations.
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(o)
6
Fire effects.
NOTE: Wave action is not included in this Standard. Where the bridge is subject to wave action, refer to specialist literature.
1.3 Special studies Where changes are made to a part or all of the design processes detailed in this Standard or new information or methods are introduced, they should be established by special studies. NOTE: For information on special studies refer to AS 5100.1 Appendix B
2 NORMATIVE REFERENCES The following are the normative documents referenced in this Standard: NOTE: Documents referenced for informative purposes are listed in the Bibliography.
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AS 1170 Minimum design loads on structures 1170.4—2007 Part 4: Earthquake actions 1530 1530.4
Methods for fire tests on building materials, components and structures Part 4: Fire-resistance test of elements of construction
1657
Fixed platforms, walkways, stairways, and ladders—Design, construction and installation
5100 5100.1 5100.3 5100.4 5100.5 5100.9
Bridge Part 1: Part 3: Part 4: Part 5: Part 9:
AS/NZS 1170 1170.2
Structural design actions Part 2: Wind actions
5100 5100.6
Bridge design Part 6: Steel and composite construction
design Scope and general principles Foundations and soil-supporting structures Bearings and deck joints Concrete Timber bridges
Austroads Guide to Road Design Guide to Traffic Management Part 3: Traffic Studies and Analysis AASHTO LRFD Bridge Design Specifications Standard Specifications for Structural Supports for Highway Signs, Luminaires and Traffic Signals Manual for Assessing Safety Hardware (MASH) 3 DEFINITIONS For the purposes of this Standard, the definitions given in AS 5100.1 and those below apply. 3.1 Air space developments A structure built over a railway or road to support overhead offices, shops, public space or accommodation. 3.2 Cantilever sign structure A sign structure supported at one end only.
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3.3 External developments A public or private structure adjacent to the road or rail corridor. 3.4 High-mast light poles Light poles with an overall height exceeding 13 m. 3.5 Portal sign structure A sign structure comprising one or more horizontal or sloped members supported by at least two vertical members. NOTE: The members may be trusses.
3.6 Rail Rail traffic includes rail freight trains, rail passenger trains, electrified trains, light rail traffic, trams and cane rail traffic. 3.7 Track category 3.7.1 Heavy haul freight (HHF) Freight rail transport carrying axle loads over 25 t.
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3.7.2 Main line freight (MLF) Freight rail transport carrying axle loads up to 25 t. 3.7.3 Branch line freight (BLF) Freight rail transport carrying axle loads below 25 t. 3.7.4 Light rail (LR) Passenger only rail transport with axle loads not exceeding 15 t, including trams. 3.8 Underground rail A rail track that is continuously enclosed above, below and both sides by structure and/or ground for a length of 80 m or greater, or as otherwise specified by the relevant rail authority. 4 NOTATION Unless a contrary intention is given, the following applies: (a)
Where non-dimensional ratios are involved, both the numerator and denominator are expressed in identical units.
(b)
The dimensional units for length and stress in all expressions or equations are to be taken as millimetres (mm), Newtons (N) and megapascals (MPa) respectively, unless specifically noted otherwise.
(c)
An asterisk (*) placed after a symbol as a superscript denotes a design action effect due to the design load for the ultimate limit state (ULS). Symbol A ALFi Ad
Adeb
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Definition axle load accompanying lane factor for the ith lane where ‘i’ equals 2 of more wetted area of the pier normal to the water flow, equal to the thickness of the pier normal to the direction of the water flow multiplied by the height of the water flow projected area of debris
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AL
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wetted area, equal to the width of the pier parallel to the direction of the water flow multiplied by the height of the water flow; or plan deck area of the superstructure
Ap
bridge area in plan
As
net wetted area of the superstructure, including any railings or barriers, projected on a plane normal to the water flow
At
area of the structure for calculation of wind load
a
maximum vertical acceleration
B
length of the bearing seat transverse to the bridge longitudinal axis
b
width between external barriers ignoring internal kerbs, median barriers and medians; or overall width of the bridge between outer faces of barriers
C(Tf)
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Cd
design action coefficient for elastic horizontal earthquake response drag coefficient
Cd (Tf)
design action coefficient
Ch (T)
acceleration spectral shape factor
Ch (Tf)
acceleration spectral shape factor at fundamental natural period of vibration of the bridge frame in the direction considered (longitudinal or transverse)
CL
lift coefficient
Cm
moment coefficient
Cs
side force coefficient (which depends on the angle between the water flow direction and the plane containing the pier)
CT
base number of load cycles
C1
coefficient dependent on the end fixity conditions
D
total depth of superstructure
Dc
section depth in the direction considered
d
depth of the superstructure, including solid barrier, if applicable; or depth below underside of sleepers; or thickness of the slab over a box cell
d bl
diameter of longitudinal reinforcement steel
d sp
wetted depth of the superstructure (including any railings or barriers) projected on a plane normal to the water flow
d ss
wetted depth of the solid superstructure (excluding any railings but including solid barriers) projected on a plane normal to the water flow
d wgs
vertical distance from the girder soffit to the flood water surface upstream of the bridge
FBM
braking force applied by multiple vehicles
FBS
braking force applied by a single vehicle
Fc
centrifugal force
Fd
design drag force
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AS 5100.2:2017
Fi
design transverse force at bridge frame mass location mi proportional to m i i
FF
bridge frame horizontal earthquake force
FL
ultimate longitudinal or transverse inward load on a barrier; or
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design lift force Fr
Froude number
FT
ultimate transverse outward load on a barrier
FV
ultimate vertical downward load on a barrier
* FLu
ultimate design lift force
f0
fundamental frequency of vibration
fsy
characteristic yield strength of flexural reinforcement
fsye
expected yield strength of flexural reinforcement
fsy.t
characteristic yield strength of lateral reinforcement
ful
characteristic ultimate strength of flexural reinforcement
f*
fatigue design stress range
f c
characteristic compressive (cylinder) strength of concrete at 28 days
f cc
confined compressive strength of concrete, which may be taken as 1.5 f c if not calculated by rational analysis
G
dead load
Gb
rail ballast and track loads
Ge
soil and groundwater loads on retaining walls and buried structures
Gs
superimposed dead load
g
acceleration due to gravity
H
pier height between the centre of plastic hinges at the top and bottom of the pier in double bending; or pier height from the centre of the plastic hinge to the point of contraflexure at top or bottom of the pier in single bending; or height from the base to the intersection of the uppermost principal horizontal members
h
depth of fill cover height of the post above the base plate
hd
average height of piers supporting the superstructure length Ld
Ki
individual pier longitudinal or transverse stiffness, expressed as force per unit longitudinal or transverse displacement at the location of mass i
k
coefficient
ke
equivalent effective stiffness of the bridge frame
kp
probability factor
L
effective span; or loaded length; or span of member between posts; or
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length from the intersection of the principal members to the tip of the cantilever arm of a cantilever sign structure
L
characteristic length
Lbs
minimum overlap length measured normal to the face of an abutment or pier
Lc
distance from the centre of the plastic hinge to the point of contraflexure in the pier
Ld
length of the superstructure to the next expansion joint
Lf
span of main girders, trusses or stringers, or cross-girder spacing for crossgirders
Lg
distance of wheel load to the track centre-line
LL
vehicle contact length for longitudinal collision load on a barrier
LLF
total length of the bridge
Lm
mean length of main girders over n continuous spans
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L max
largest of the values L1 , L2 , ……Ln
Lp
plastic hinge length
Lsp
strain penetration length for reinforced concrete piers
LT
vehicle contact length for transverse collision load on a barrier
Lv
distance between centres of axle groups vehicle contact length for vertical loads on a barrier
L1 , L2 , Ln
span lengths of a continuous structure
L
characteristic length
Mg
design superstructure moment due to water flow
Ms
shielding multiplier
* M Lu
ultimate moment due to water flow and/or debris loading, as applicable
me
effective mass of the bridge frame
mi
one of the n individual masses representing the bridge frame
N*
pile ultimate axial force
N
duration of construction, in years
n
number of standard design lanes; or effective number of stress cycles; or number of continuous main girder spans
nT
number of equivalent stress cycles of amplitude (f* ) per train
P
annual probability of exceedance
PS
prestress effect
Pr
proximity ratio
Q
traffic loading from road, rail, pedestrian, cyclist path or maintenance traffic
R
return period
R
damping modifier
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r
radius of curve
Sr
relative submergence
T
period of vibration; or
AS 5100.2:2017
temperature
Tf
fundamental natural period of the bridge; or bridge frame fundamental natural period in the direction considered
t
thickness of the deck
V
design traffic speed; or velocity of water flow
Vi
shear force of the ith element of the bridge
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seismic shear force at the top of pier or abutment component i
Vs
design wind speed for serviceability limit state (SLS)
Vu
design wind speed for ultimate limit state (ULS)
WBM
load due to multiple lanes of the M1600 moving traffic load for the length under consideration
WBS
load due to a single lane of the M1600 moving traffic load for the length under consideration
Wc
load due to multiple standard design lanes of the M1600 moving traffic load for the length under consideration
Wi
one of the n individual weights representing the bridge frame
Wt
serviceability design transverse wind load
Wt*
ultimate design transverse wind load
Wv
serviceability design vertical wind load
* v
W
y
ultimate design vertical wind load average flow depth; or static displacement due to design pedestrian load; or variable distance taken in determining temperature change at T(y)
ygs
average vertical distance from the girder soffit to the bed assuming no scour at the span under consideration
Z
design seismic hazard factor; or bearing layout modulus
dynamic load allowance (DLA)
logarithmic decrement of decay of vibration
b
displacement capacity at superstructure resulting from the pier-cap bearing deformation
c
displacement capacity of the first bridge frame pier or abutment to reach displacement capacity
d
ductile displacement capacity
f
displacement capacity at superstructure resulting from foundation deformation
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AS 5100.2:2017
i
transverse displacement capacity of a bridge pier or abutment
p
inelastic displacement capacity
y
yield displacement capacity
Fi b , f, s
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12
transverse displacement at bridge frame mass location mi due to the application of Fi bearing, foundation and pier structural displacement, respectively
d
ductile seismic displacement demand
e
corner-period elastic seismic displacement demand
e(T)
elastic seismic displacement demand for horizontal earthquake response
e(Tf)
elastic seismic displacement demand for the bridge frame fundamental natural period in the direction considered
h(T)
elastic seismic displacement spectral shape factor
i
ductile seismic displacement demand at the top of pier or abutment component i
k
characteristic horizontal seismic displacement demand of the bridge frame
L
longitudinal seismic displacement at the abutment
εsd
tensile strain limit in flexural reinforcement; or tensile strain in reinforcing steel
εsul
strain at maximum stress of flexural reinforcement
εsut
strain at maximum stress of lateral reinforcement
εy
strain at the expected yield strength of the flexural reinforcement (or structural steel)
g
load factor for dead load
gb
load factor for rail ballast and track loads
ge
load factor for soil and groundwater loads
gs
load factor for superimposed dead load
Q
load factor for traffic load
WF
ultimate load factor for forces resulting from water flow
design ductility factor
d
displacement ductility
b , f, s
bearing, foundation and pier structural damping, respectively
e
bridge frame equivalent viscous damping ratio corresponding to the design ductility level of response
i
elastic viscous damping
super elevation of the road
p
plastic rotation capacity at the plastic hinge
w
angle between the direction of the water flow and the transverse centre-line of the pier
s
volumetric ratio of lateral (transverse) reinforcement
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AS 5100.2:2017
ϕc
value of normalised fundamental displacement mode shape at the first bridge frame pier or abutment to reach displacement capacity
ϕe
characteristic value of the fundamental mode shape of the bridge frame
ϕi
value of normalized fundamental displacement mode shape at pier or abutment
ϕls
ductile curvature corresponding to the strain limit at the relevant design performance level
ϕy
yield curvature
dynamic response factor
5 MATTERS FOR RESOLUTION BEFORE DESIGN COMMENCES
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The matters for resolution listed below shall, where relevant, be confirmed as accepted by the relevant authority before commencing the design process. 1
Approval to vary any of the loads set out in this Standard, provided the provisions of AS 5100.1 are complied with (Clause 1.2).
2
Design loads and factors for road bridges carrying rail traffic (Clause 7.4).
3
Load factors for centrifugal and braking loads from heavy load platforms, when applicable (Clause 7.10).
4
Approval of an analytical procedure for the distribution of road traffic loads through fill (Clause 7.12).
5
Design load for a pedestrian or cyclist path bridge that is also used for maintenance, inspection or emergency vehicle access (Claus e 8.1).
6
Design loads for rail bridges carrying cane rail traffic and/or other special applications (Clause 9.1).
7
Approval to use the rational method for braking and traction forces (Clause 9.7.2 and 9.7.2.3).
8
Bridge-specific design parameters to be used in applying the rational method for braking and traction forces (Clause 9.7.2.3).
9
Approval of a risk analysis for road bridges designed with an alternative load path under collision load (Clause 11.1).
10
Approval of a risk analysis for bridge supports located between 10 m and 20 m from the centre-line of a rail track (Clause 11.4.2.4).
11
Approval of a dynamic collision analysis (Clause 11.4.4.2).
12
Recommendation of the type of vessel, weight of vessel and speed of impact on a bridge for collision from waterway traffic, and approval of the proposed design vessel and speed (Clause 11.6).
13
Approval of the minimum equivalent static ship impact force applicable to piers in navigable waterways (Clause 11.6).
14
Specification of the ultimate design load, load distribution length and minimum effective height for special barrier performance levels (Clause 12.2.2 and 12.2.3).
15
Approval of a load transfer mechanism across a movement joint in a rigid barrier (Clause 12.4.2).
16
Approval of a detailed dynamic analysis (Clause 13.2.3).
17
Approval of a vibration assessment of a rail bridge, when required (Clause 13.3).
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18
Bridge earthquake design category classification (Clause 15.4.1).
19
Approval of large items for flood impact (Clause 16.7.3).
20
Construction design load criteria for other types of bridge construction (Table 22.2.2).
21
Approval of the average recurrence interval for wind load on noise barriers and protection screens (Clause 25.3.2).
6 DEAD LOADS (G) 6.1 General
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The nominal dead load shall be calculated from the dimensions shown on the drawings and the mean value of the weight per unit volume of the materials. A value based on the densities of the materials, the percentage of reinforcement and other appropriate factors shall be adopted. Wherever possible, design densities shall be based on measurements of the materials to be used. NOTES: 1 The weights per cubic metre given in Tables 6.1(A) and 6.1(B) may be used in calculating the nominal dead load unless a more precise determination has been made. Where a range of values is given, calculations should be performed using the extremes of the expected range and the most critical case used for design. 2 For other materials, refer to AS 1170.1.
Selecting a high value of density may be conservative when considering some limit states, but may not be conservative when considering stability, stresses at transfer of prestress and the like. If insufficient information is available to accurately assess the mean weight per unit volume, calculations shall be performed using a range of values and the most critical case shall be used for the design. The density of reinforced concrete shall take account of variations in aggregate density and shall allow for the mass of included reinforcement. To ensure that the structure satisfies minimum strength and stability criteria, an ultimate load combination comprising only dead load, superimposed dead load, rail ballast and track load and soil and groundwater load shall be considered. The load factors for this load combination shall be in accordance with Clause 23.2.
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AS 5100.2:2017
TABLE 6.1(A) WEIGHT FOR NOMINATED DEAD LOADS Material Aluminium alloy
26.7
Bituminous wearing surface, asphalt
22.0
Ballast for railways
19.0
Compacted earth filling Compacted gravel, road metal Concrete, unreinforced (add 0.6 for each 1% by volume of steel reinforcement and tendons)
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Weight per cubic metre kN/m 3
22.0 (see Note 1) 19.0–23.0 See Table 6.1(B)
Masonry
23.5
Neoprene
11.3
Sand, fine (dry)
15.5–17.5
Sand, coarse (dry)
18.0–19.5
Sand (saturated)
22.5
Steel and other ferrous metals
77.0
Timber, softwood
7.0 (see Note 2)
Timber, hardwood
11.0 (see Note 2)
Water, fresh
9.8
Water, salt
10.0
NOTES: 1
A value of 22 kN/m3 for unit weight of fill is used for normal fill material; however, the unit weight of soils of volcanic origin (e.g. pumice sand at 14 kN/m3 ) may be significantly lower and the unit weight of soils of oxide origin (e.g. iron ore at 27 kN/m3 ) may be significantly higher.
2
For the unit weight of particular timber species, refer to AS 5100.9.
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TABLE 6.1(B) WEIGHT PER CUBIC METRE OF UNREINFORCED CONCRETE Typical coarse aggregates
Adelaide quartzite, Brisbane gravel, Perth granite, Sydney gravel
Density of coarse aggregates kg/m 3
Cement content kg/m 3
Weight per cubic metre kN/m 3
450
24.0
330
22.5
450
24.5
330
23.0
450
25.5
330
24.0
450
26.0
330
25.0
2500
2700
Melbourne basalt, Sydney basalt 2900 Hobart dolerite 3100
NOTE: The values given in the Table apply to normal concrete, have no added air and the accuracy is approximately 0.5 kN/m3 .
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6.2 Dead load of structure Dead load shall be considered as the weight of the parts of the structure that are structural elements and any non-structural elements that are considered unlikely to vary during construction and use of the structure, such as barriers and kerbs of steel or concrete. To obtain the design dead loads for ULS and SLS, the nominal dead load shall be multiplied by the appropriate load factor for dead load (g ) given in Table 6.2. The appropriate value of g shall be applied to the dead load of all parts of the structure. TABLE 6.2 LOAD FACTORS FOR DEAD LOAD OF STRUCTURE ( g ) Type of material
ULSs where dead load
SLSs
Reduces safety
Increases safety
Steel
1.10
0.90
1.0
Concrete
1.20
0.85
1.0
Concrete at transfer of prestress
1.15
0.90
N/A
Timber
1.25
0.80
1.0
NOTE: For precast members, where— (a)
appropriate control and monitoring are exercised over dimensions and mass; and
(b)
the value for reinforced concrete density is based upon the measured density of the concrete to be used and accurate estimates of reinforcement inclusion,
the relevant authority may approve a reduction of load factor to not less than 1.1 for ULSs for the cases where the dead load reduces safety.
6.3 Superimposed dead load (Gs) Superimposed dead load shall be considered as the weight of all materials forming the loads on the structure which are not structural elements and which vary during construction and use of the structure. NOTE: Examples of superimposed dead load include surfacing material, footway filling, pipes, conduits, cables and other utility services, and additional concrete to compensate for the hog of prestressed beams.
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AS 5100.2:2017
If a separate wearing surface is to be placed when the bridge is constructed or if placement of a separate wearing surface is anticipated in the future, allowance shall be made for its weight in the superimposed dead load. The design of superimposed dead loads for ultimate and SLSs shall be obtained by applying the appropriate load factor (gs), given in Table 6.3, to the nominal superimposed dead loads on the structure. For special cases, and subject to approval of the relevant authority, the values of gs to be applied to the nominal superimposed dead load may be reduced to an amount not less than those given in Item (b) of Table 6.3, provided the nominal superimposed dead load is not exceeded during the life of the bridge. TABLE 6.3 LOAD FACTORS FOR SUPERIMPOSED DEAD LOAD ( gs) ULSs where Gs Type of structure
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(a) All structures, except for Item (b) (b) Special cases Where specified by the relevant authority for major structures and superimposed dead loads are controlled.
Type of load
Reduces safety
Increases safety
Permanent Removable
2.0 2.0
0.7 0.0
1.3 1.3
Permanent Removable
1.4 1.4
0.8 0.0
1.0 1.0
SLSs
6.4 Soil and groundwater loads on retaining walls and buried structures (Ge) The design of foundations and soil-supporting structures shall be carried out in accordance with this Standard and AS 5100.3. The soil and groundwater loads shall be factored by the load factor (ge) given in Table 6.4. TABLE 6.4 LOAD FACTORS FOR SOIL AND GROUNDWATER LOADS ( ge) Type of soil
ULSs where soil Reduces safety
Increases safety
SLSs
Controlled fill with regular testing of soil density
1.25
0.85
1.0
All other fills and in situ soils
1.5
0.7
1.2
Groundwater
1.0
1.0
1.0
NOTE: Variation in water levels shall be taken into account by using design levels based on a return period of 1000 years for the ULS or 100 years for the SLS.
6.5 Rail ballast and track loads (Gb) Rail ballast and track shall be considered as superimposed dead loads. The design loads for the ULS and SLS shall be obtained by applying the appropriate load factor (gb ) given in Table 6.5 to the nominal ballast and track loads. For bridges where it is possible to fill with ballast to a much greater depth than normally specified, the maximum amount of ballast possible on the bridge shall also be determined and the nominal amount of ballast shall be taken as not less than 0.7 times that maximum amount.
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AS 5100.2:2017
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TABLE 6.5 LOAD FACTORS FOR RAIL BALLAST AND TRACK LOADS ( gb) Type of structure
All structures
Type of load
ULSs where Gbs
SLSs
Reduces safety
Increases safety
Ballast and track
1.7
0.7
1.3
Transom track
1.4
0.9
1.2
7 ROAD TRAFFIC (Q) 7.1 General Road traffic load is the load resulting from the passage of vehicles, either singly or in groups, or pedestrians. The magnitude, direction and positioning of loads in this Standard produce effects in structures that approximate the effects of vehicles or groups of vehicles. The load models are not intended to be the same as actual vehicles.
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All road bridges shall be designed to resist the following: (a)
The traffic loads specified in this Standard, which approximate the effects induced by moving traffic, stationary queues of traffic and pedestrian traffic.
(b)
The most adverse effects induced by the following loading elements, combinations of these elements and their corresponding load factors: (i)
W80 wheel load.
(ii)
A160 axle load.
(iii) M1600 moving traffic load. (iv)
M1600 moving tri-axle group load.
(v)
S1600 stationary traffic load.
(vi)
HLP320 or HLP400, if specified by the relevant authority.
(vii) Dynamic load allowance (). (viii) Number and position of traffic lanes. (ix)
Accompanying lane factors (ALF).
(x)
Centrifugal forces (Fc).
(xi)
Braking forces (FBS, FBM).
(xii) Fatigue load. (xiii) Pedestrian load. 7.2 SM1600 loads 7.2.1 General The abbreviation SM1600 represents the design loads W80, A160, M1600, M1600 tri-axle group and S1600 traffic design loads. NOTE:Appendix C tabulates values of bending moment and shear force due to SM1600 loading.
7.2.2 W80 wheel load The W80 wheel load models an individual heavy wheel load. The W80 wheel load shall consist of an 80 kN load uniformly distributed over a contact area of 400 mm 250 mm. It shall be applied anywhere on the roadway surface and to all structural elements for which the critical load is a single wheel load. Standards Australia
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AS 5100.2:2017
7.2.3 A160 axle load The A160 axle load models an individual heavy axle. The A160 axle load shall be positioned laterally within a 3.2 m standard design lane, as shown in Figure 7.2.3.
16 0 k N
ELE VATIO N 0.4 3 . 2 m st an d ar d design lane
2.0
0. 25
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PL AN DIMENSIONS IN METRES
FIGURE 7.2.3 A160 AXLE LOAD
7.2.4 M1600 moving traffic load The M1600 moving traffic load models the loads applied by a moving stream of traffic. The M1600 load shall be positioned laterally within a 3.2 m standard design lane as shown in Figure 7.2.4. The moving traffic load shall consist of a uniformly distributed load together with the axle group loads as shown in Figure 7.2.4. The uniformly distributed component of the M1600 moving traffic load shall be continuous under the axle group loads and shall be considered as uniformly distributed over the width of a 3.2 m standard design lane. The uniformly distributed component of the M1600 moving traffic load shall be continuous or discontinuous and of any length as may be necessary to produce the most adverse effects. Likewise, the axle group loads position and variable spacing shall be determined such as to produce the most adverse effects. Where a single tri-axle group from the M1600 moving traffic load (including the UDL component) is considered, the dynamic load allowance ( ) shall be as given in Table 7.7.2. The UDL component shall be continuous or discontinuous and of any length as may be necessary to produce the most adverse effects.
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AS 5100.2:2017
20 360 kN
360 kN
360 kN
360 kN
6 k N /m ELE VATIO N 1. 25 1. 25
3 .75
1. 25 1. 25 Varies 6. 25 min. 1. 25 1. 25
5.0
0. 2
1. 25 1. 25
0.6
2.0
0.4
3 . 2 m st an d ar d design lane
0.6
PL AN DIMENSIONS IN METRES
FIGURE 7.2.4 M1600 MOVING TRAFFIC LOAD
7.2.5 S1600 stationary traffic load
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The S1600 stationary traffic load models the loads applied by a stationary queue of traffic. The S1600 stationary traffic load shall consist of a uniformly distributed load together with axle group loads as shown in Figure 7.2.5. The uniformly distributed component of the S1600 stationary traffic load shall be continuous under the axle group loads and shall be considered as uniformly distributed over the width of a 3.2 m standard design lane. The S1600 stationary load shall be positioned laterally within a 3.2 m standard design lane as shown in Figure 7.2.5. The uniformly distributed component of the S1600 stationary traffic load shall be continuous or discontinuous and of any length as may be necessary to produce the most adverse effects. Likewise, the axle group load position and variable spacing shall be determined such as to produce the most adverse effects.
24 0 k N
24 0 k N
24 0 k N
24 0 k N
24 k N /m ELE VATIO N 1. 25 1. 25
3 .75
1. 25 1. 25 Var ies 6. 25 min. 1. 25 1. 25
0. 2
5.0
1. 25 1. 25
0.6
2.0
0.4
3 . 2 m st an d ar d design lane
0.6
PL AN DIMENSIONS IN METRES
FIGURE 7.2.5 S1600 STATIONARY TRAFFIC LOAD
7.3 Heavy load platform The heavy load platform design load HLP 320 or HLP 400, or an alternative platform design load, may be specified by the relevant authority. Details of HLP 320 and HLP 400 are given in Figure 7.3.
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AS 5100.2:2017
The HLP 320 and HLP 400 heavy load platform shall be positioned within two standard design lanes. The heavy load platform shall be positioned up to 1.0 m laterally from the centre of two standard design lanes. The two standard design lanes shall be positioned laterally to create the worst effect unless otherwise specified by the relevant authority. For bridges with three or more standard design lanes, the unobstructed standard design lanes shall be loaded with half of either M1600 moving traffic load or the S1600 stationary traffic load, to create the worst effect, unless the relevant authority specifies otherwise. Accompanying lane factor for S1600 and M1600 is not applicable to this Clause.
16 a x l e s, s pac e d at 1.8 m c e ntre s
Tot al l oad p er a x l e
20 0 k N H LP 3 20 25 0 k N H LP 4 0 0
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ELE VATIO N VIE W 500
14 0 0
500
14 0 0 3 6 0 0 for H LP 3 20 4 5 0 0 for H LP 4 0 0
EN D VIE W OF AN H LP A XLE DIMENSIONS IN MILLIMETRES
FIGURE 7.3 LATERAL SPACING OF DUAL WHEELS ALONG AN AXLE FOR HLP LOADS
7.4 Rail traffic Where road bridges are to carry rail traffic, the operating authority for the utility shall be consulted to determine the appropriate design loads and load factors. 7.5 Standard design lanes The A160, M1600 and S1600 loadings shall be assumed to occupy one standard design lane of 3.2 m width. The number of standard design lanes shall be as follows:
n =
b (rounded down to next integer) 3 .2
. . . 7.5
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b = width between external barriers ignoring internal kerbs, median barriers and medians The full width between external barriers on the bridge shall be designed for road traffic to allow for future changes to lane markings, unless otherwise specified by the relevant authority. These standard design lanes shall be positioned laterally on the bridge to produce the most adverse effects. 7.6 Accompanying lane factors If more than one lane is loaded, the A160, M1600, S1600, M1600 tri-axle load or light rail loading applied to the additional lanes shall be multiplied by the accompanying lane factors given in Table 7.6. The number of standard design lanes loaded and the load patterning (standard design lane numbering) shall be selected to produce the most adverse effects.
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For bridges that support vehicle and pedestrian, cyclist path or maintenance traffic, the accompanying lane factors shall be applied to both the vehicle and pedestrian, cyclist path or maintenance traffic. The pedestrian, cyclist path or maintenance load shall be considered as one standard design lane. For bridges supporting both road and light rail traffic, each light rail track shall be considered as one standard design lane. TABLE 7.6 ACCOMPANYING LANE FACTORS Standard design lane number (n) Accompanying lane factor (ALF i ) 1 lane loaded
1.0
2 lanes loaded
1.0 for first lane; and 0.8 for second lane
3 or more lanes loaded
1.0 for first lane; 0.8 for second lane; and 0.4 for third and subsequent lanes
NOTES: 1
First lane—the loaded lane giving the largest effect.
2
Second lane—the loaded lane giving the second largest effect.
3
Third lane—the loaded lane giving the third largest effect.
7.7 Dynamic load allowance 7.7.1 General The dynamic load allowance ( ) set out in this Clause specifies an increase in the traffic load resulting from the interaction of moving vehicles and the bridge structure. It shall be described in terms of the static equivalent of the dynamic and vibratory effects. For design purposes, shall be specified as a proportion of the traffic load and shall be applied as specified in Clause 7.7.2. The dynamic load allowance applies to both the ULS and SLS. The dynamic load allowance models the dynamic effects of vehicles moving over bridges with typical road profile irregularities. 7.7.2 Magnitude The design action is equal to (1 + ) the load factor the action under consideration. The value of for the appropriate loading shall be as given in Table 7.7.2. For deck joints, the values for specified in AS 5100.4 shall be used. Standards Australia
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AS 5100.2:2017
TABLE 7.7.2 DYNAMIC LOAD ALLOWANCE ( ) Loading
Dynamic load allowance ( )
W80 wheel load
0.4
A160 axle load
0.4
M1600 tri-axle group (see Note 1)
0.35
M1600 (see Note 1)
0.30
S1600 (see Note 1)
0.0
Heavy load platform (see Note 2)
0.1
Centrifugal force, braking force or pedestrian load
0.0
NOTES: 1
Including the UDL component of the traffic load.
2
A heavy load platform travels at a maximum speed of 10 km/h. A higher dynamic load allowance ( ) may apply where this speed is exceeded.
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7.7.3 Application The dynamic load allowance ( ) shall be applied to all parts of the structure extending down to the ground level. For parts of the structure below the ground level, the dynamic load allowance to be applied to each part shall be— (a)
the ground level value for a cover depth of zero;
(b)
zero for a cover depth of 2 m or more; or
(c)
a linear interpolation between depths of zero and 2 m.
Consideration shall be made of the depth of possible scour when determining ground level. For buried structures such as pipes, culverts and soil-steel structures, the dynamic load allowance to be applied to the entire structure shall be— (i)
the ground level value for a cover depth of zero;
(ii)
0.1 for a cover depth of 2 m or more for loads excluding S1600. For S1600 loads, the dynamic load allowance is zero; or
(iii) a linear interpolation between depths of zero and 2 m. 7.7.4 Dynamic load reversal Consideration shall be given to the reversal of the dynamic response to traffic load. (Vibrations may continue and slowly decay after passing of traffic.) In particular, the minimum reaction on bearings shall take into consideration any reduction that may occur as a result of dynamic effects. 7.8 Horizontal forces 7.8.1 Centrifugal forces For bridges on horizontal curves, allowance shall be made for the centrifugal effects of traffic load on all parts of the structure. The bridge shall be designed to resist the most adverse co-existing effects induced by the M1600 moving traffic load and the centrifugal force (F c), in kilonewtons.
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The centrifugal force (F c) shall be assumed to act at deck level and shall be applied in accordance with the distribution of load for the M1600 moving traffic load. The centrifugal force (Fc) shall be calculated as follows: Fc
=
V2 Wc rg
. . . 7.8.1(1)
(0.35 + )Wc
. . . 7.8.1(2)
where V
= design traffic speed, in metres per second
r
= radius of curve, in metres
g
= acceleration due to gravity (9.81 m/s2 )
Wc
= load due to multiple standard design lanes of the M1600 moving traffic load for the length under consideration, in kilonewtons No dynamic load allowance shall be considered. Accompanying lane factors shall be applied, i.e.— n
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=
ALF M1600 i 1
i
i
. . . 7.8.1(3)
where n
= number of standard design lanes
ALFi = accompanying lane factor (see Table 7.6)
= super elevation of the road, expressed as a ratio (e.g. 4% superelevation is expressed as 0.04 and adverse super elevation is negative)
7.8.2 Braking forces
Braking effects of traffic shall be considered as a longitudinal force. Braking forces shall be applied in either direction. The restraint system shall be designed to resist the most adverse co-existing effects induced by the braking force and the M1600 traffic load. The braking force shall be applied in accordance with the distribution of the M1600 traffic load. The braking force shall be assumed to act at the road surface. The number and lateral position of the standard design lanes on the bridge shall be selected to produce the most adverse effects. The most adverse effects from the following scenarios shall be considered: (a)
Single standard design lane The braking force (FBS) applied in a single standard design lane shall be calculated as follows: FBS = 0.45WBS
. . . 7.8.2(1)
200 kN < FBS < 720 kN where WBS = load due to a single lane of the M1600 moving traffic load for the length under consideration, in kilonewtons, up to a maximum of 1600 kN No dynamic load allowance shall be included. FBS shall be applied to any lane of a multi-lane bridge to produce the most adverse effects. Standards Australia
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(b)
AS 5100.2:2017
Multiple standard design lanes The total braking force (FBM) applied in multiple standard design lanes shall be calculated as follows: FBM = 0.15WBM
. . . 7.8.2(2)
200 kN < FBM < 1200 kN where WBM = load due to multiple standard design lanes of the M1600 moving traffic load for the length under consideration, in kilonewtons, up to a maximum of 8000 kN No dynamic load allowance shall be included. Accompanying lane factors shall be applied, that is— n
=
ALF M1600 i 1
i
i
. . . 7.8.2(3)
where n
= number of standard design lanes
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ALFi = accompanying lane factor for ith lane where ‘i’ equals 2 or more (see Table 7.6) The number of standard design lanes to be included shall be limited to those likely to carry traffic in a single direction, unless otherwise specified by the relevant authority. When assessing the effects of longitudinal forces on bridge bearings and substructures, the friction or shear displacement characteristics of expansion bearings and the stiffness of the substructure shall be taken into account. 7.9 Fatigue load effects
The fatigue design traffic load effects shall be determined from 70% of the effects of a single A160 axle or 70% of a single M1600 moving traffic load, without UDL, whichever is more severe. In both cases, a load factor of 1.0 shall be used and the load effects shall be increased by the dynamic load allowance ( ). The single A160 axle load or M1600 moving traffic load, without UDL, shall be placed within any design traffic lane to maximize the fatigue effects for the component under consideration. Unless otherwise specified by the relevant authority, the number of fatigue stress cycles to be used for the calculation of the fatigue capacity of the structural element under consideration shall be as follows: (a)
For the fatigue design load of 0.70 (A160 axle load) (1 + ): (current number of heavy vehicles per lane per day) 4 104 (route factor).
(b)
For the fatigue design load of 0.70 (M1600 moving traffic load without UDL) (1 + ): (current number of heavy vehicles per lane per day) 2 104(L0.5) (route factor).
where L is the effective span, in metres, and is defined as follows: (i)
For positive bending moments, L is the actual span in which the bending moment is being considered.
(ii)
For negative moment over interior supports, L is the average of the adjacent spans.
(iii) For end shear, L is the actual span. (iv)
For reactions, L is the sum of the adjacent spans.
(v)
For cross-girders, L is twice the longitudinal spacing of the cross-girders.
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Unless otherwise specified by the relevant authority, the route factor shall be— (A)
for principal interstate freeways and highways .......................................................1.0;
(B)
for urban freeways .................................................................................................0.7;
(C)
for other rural routes ....................................................................................... 0.5; and
(D)
for urban roads other than freeways ....................................................................... 0.3.
On interstate and other rural routes where there are two or more lanes in one direction, the number of heavy vehicles per lane per day shall be the total of the heavy vehicles travelling in that direction. On urban routes where there are two or more lanes in one direction, the number of heavy vehicles per lane per day shall be 65% of the total number of heavy vehicles in that direction. The fatigue design traffic load effects and relevant stress cycles shall be applied to each design lane independently. A fatigue stress cycle shall be taken to be the maximum peak to peak stress from the passage of the relevant fatigue design load.
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Heavy vehicles shall be as defined by the Austroads Guide to Traffic Management, Part 3: Traffic Studies and Analysis, Table A8, i.e., Classes 3 to 12. The current number of heavy vehicles shall be based on the year the bridge is to be put into service. This Clause does not apply to fatigue design of roadway deck joints. 7.10 Load factors For ultimate, serviceability and fatigue limit state design loads, the load factors for design road traffic loads shall be as given in Table 7.10(A). The load factor to be applied in calculating the design centrifugal and braking forces, excluding HLP loads, shall be as given in Table 7.10(B). The HLP load factors shall be specified by the relevant authority. Each of the design horizontal forces due to road traffic load shall be applied separately but in combination with the coexisting M1600 traffic load and such load cases or any combination thereof shall be considered as a single vehicular traffic load specified in Clause 23.1.4.
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AS 5100.2:2017
TABLE 7.10(A) LOAD FACTORS FOR DESIGN ROAD TRAFFIC LOADS ( Q) Limit state
Loading
Ultimate
Serviceability
Fatigue
W80 wheel
1.8
1.0
0.0
A160 axle
1.8
1.0
1.0 (see Note 1)
M1600
1.8
1.0
1.0 (see Notes 1 and 2)
S1600
1.8
1.0
0.0
Heavy load platform (HLP)
1.5
1.0
0.0
Half of SM1600 traffic load in unobstructed lanes when applied in conjunction with HLP loading
1.8
1.0
0.0
NOTES: 1
70% of traffic load.
2
Excludes uniformly distributed load.
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TABLE 7.10(B) LOAD FACTORS FOR DESIGN CENTRIFUGAL AND BRAKING FORCES ( Q) Force
Limit state Ultimate
Serviceability
Centrifugal force
1.8
1.0
Braking force
1.8
1.0
7.11 Deflection of superstructure
The deflection limits of a road bridge under traffic for the SLS shall be appropriate to the structure and its intended use, the nature of the loading and the elements supported by it. Notwithstanding this requirement, the deflection for the SLS under traffic load plus dynamic load allowance shall be not greater than 1/600 of the span or 1/300 of the cantilever projection, as applicable. The traffic load to be used for calculating deflection shall be one M1600 moving traffic load, without UDL, including dynamic load allowance, placed longitudinally in each design lane to produce the maximum deflection, taking into account the accompanying lane factors. NOTE: In calculating the deflection, the following assumptions may be made: (a) The deflection of the bridge may be averaged across all beams. (b) The design cross-section of the bridge may include continuous portions of permanent road furniture contributing to stiffness, provided adequate connection is included to ensure composite action with the bridge deck.
In addition, road traffic bridges shall be designed so that— (a)
deflections do not infringe on clearance diagrams;
(b)
hog deflection does not exceed 1/300 of the span; and
(c)
no sag deflection occurs under permanent loads.
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7.12 Distribution of road traffic loads through fill
For all types of roadway pavements and fill above buried structures, the distribution of SM1600 design loads, with the factors and allowances applied in accordance with this Standard, shall be as specified below, unless calculated otherwise by an analytical modelling procedure approved by the relevant authority. This requirement shall apply to all types of roadway pavements. SM1600 design wheel loads shall be distributed through the fill cover over the structure, from the imprint of the rectangular wheel contact area at the road surface to a rectangular distribution area on the surface of the structure, proportioned in accordance with the wheel contact area dimensions. The length of the sides of the distribution rectangle shall be determined as follows: (a)
For depths of fill cover from 0 to 200 mm—sides of distribution rectangle = sides of wheel contact rectangle + 0.5 h, where h is the depth of fill cover in millimetres.
(b)
For depths of fill cover greater than 200 mm—sides of distribution rectangle = sides of wheel contact rectangles + 100 mm + 1.2 (h – 200).
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Where distribution areas from several wheel loads overlap, the total load may be considered to be evenly distributed on the surface over the total area of distribution. The uniformly distributed component of the SM1600 design load shall be applied with no longitudinal distribution. Transverse distribution shall be as for wheel loads. The total width of transverse distribution shall not exceed the total width of the structure supporting the fill.
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a
Re c t ang ular wheel c o nt ac t area at t h e road sur fac e
AS 5100.2:2017
b
Re c t ang ular d i str i butio n area o n t h e sur fac e of t h e str u c ture
h
ℓ t = b + 10 0 + [ 1. 2 x ( h - 20 0 )]
ℓ i = a + 10 0 + [ 1. 2 x ( h - 20 0 )]
D ire c t i o n of tr ave l (a) For d e pt h s of fill greater t han 20 0
b a
Re c t ang ular wheel c o nt ac t area at t h e road sur fac e
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O ver l a p of d i s tr i b u t i o n area
h
ℓi
ℓt Tot al l oad d i str i bute d eve nly over area ( ℓ t x ℓ i )
D ire c t i o n of tr ave l
(b) O ver l a p p in g l oad d i str i but i o n area s LEGEND: a, b = lengths of the sides of the wheel contact area ℓ i , ℓ t = lengths of the sides of the distribution area on the surface of the structure h = depth of fill (depth from road surface to surface of the structure)
FIGURE 7.12 WHEEL LOADS THROUGH FILL
8 PEDESTRIAN, CYCLIST PATH AND MAINTENANCE TRAFFIC (Q) 8.1 Pedestrian and cyclist path loads
Pedestrian, cyclist path or combined (that is, shared path) bridges, ramps and stairs, independent or part of a road and/or rail traffic bridges that provide public access shall be designed for the following, unless otherwise specified by the relevant authority: (a)
The load per square metre of loaded area shall be as shown in Figure 8.1. The loaded area shall be the area related to the structural element under consideration.
(b)
Where the relevant authority specifies that the bridge be designed for crowd loading, such as for special events, a minimum design load of 5 kPa shall be used.
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(c)
Where it is possible for a light vehicle not exceeding 4.5 t to access the pedestrian or cyclist path bridge, the bridge shall be designed to carry a concentrated load of at least 20 kN on an area of 200 mm 200 mm, with no dynamic load allowance.
(d)
Stairs treads and landings shall be designed for the more severe of the following live loads: (i)
Uniformly distributed load of 5.0 kPa. or
(ii)
Point load of 4.5 kN. or
(iii) Line load of 2.2 kN/m. (e)
Where it is required for maintenance, inspection or emergency vehicles to access the bridge, the loading shall be specified by the relevant authority.
For p e d e str i an an d cyc li st pat h br i d g e s in d e p e n d e nt of t h e road or r ailway br i d g e su p er str u c ture 5
LOAD INTENSIT Y, kPa
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NOTES: 1 For barrier loading, see Clause 12.5. 2 The dynamic load allowance () is 0.0 (see Table 7.7.2).
4
3
2 For p e d e str i an an d c yc li s t p at h s at t ac h e d to t h e road or r ailway br i d g e su p er str u c ture
1
0
10
85
10 0
LOADED ARE A , m 2
FIGURE 8.1 PEDESTRIAN AND CYCLIST PATH LOADS
8.2 Maintenance load on service walkways not intended for public use
For rail bridges fitted with a service walkway or service platform, the minimum load shall be 5 kPa, unless otherwise specified by the relevant authority. For all other structures fitted with a service walkway or service platform, loads shall be determined in accordance with AS 1657, unless otherwise specified by the relevant authority. 8.3 Load factors
For ULS and SLS design loads, the load factors for design pedestrian, cyclist path and maintenance loads shall be as given in Table 8.3.
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TABLE 8.3 LOAD FACTORS FOR DESIGN PEDESTRIAN, CYCLIST PATH AND MAINTENANCE TRAFFIC LOADS ( Q) Loading Pedestrian, cyclist path and maintenance load
Limit state Ultimate
Serviceability
1.5
1.0
8.4 Deflection
For pedestrian and cyclist path bridges, the deflection under the SLS traffic load shall be not greater than 1/600 of the span or 1/300 of the cantilever projection, as applicable. The traffic load to be used for calculating deflection shall be in accordance with Clause 8.1.
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In addition, pedestrian and cyclist path bridges shall be designed so that— (a)
deflections under all SLS load cases do not infringe on clearance diagrams;
(b)
deflections under permanent effects do not permit ponding of water on the bridge;
(c)
where a hog deflection under permanent effects applies, it does not exceed 1/300 of the span; and
(d)
no sag deflection occurs under permanent loads.
9 RAIL TRAFFIC (Q) 9.1 General
Rail bridges shall be designed for the loads specified in this Clause (9), unless otherwise specified by the rail authority. Bridges carrying cane rail traffic and/or other special applications shall be designed for loads specified by the relevant authority. 9.2 300LA design rail traffic load
The 300LA load consists of a number of simulated axle groups with four axles, each having a load of 300 kN, and axle spacings of 1.7 m, 1.1 m and 1.7 m. To simulate coupled locomotives, a 360 kN axle load shall be added 2 m in front of the first simulated axle group, as shown in Figure 9.2(A). The spacing between the centres of each simulated axle group shall vary between 12 m and 20 m to give maximum effect in the member under consideration, as shown in Figure 9.2(B). NOTE: Appendix C tabulates values of bending moment and shear force due to 300LA loading.
The position of the loads and the number of axle groups shall be selected to give maximum load effects in the member under consideration.
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32 SIM U L ATED A XLE GROUP
300 kN
COUPLER
300 kN
1.7
SIM U L ATED LO CO M OTIVE 300 kN
300 kN
1.1
1.7
360 kN
2.0
DIMENSIONS IN METRES
FIGURE 9.2(A) 300LA RAIL TRAFFIC LOADS—AXLE LOADS
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SIM U L ATED A XLE GROUP
12 to 20 ( Var i e s)
12 to 20 ( Var i e s)
SIM U L ATED LO CO M OTIVE
12 to 20 ( Var i e s)
12 to 20 ( Var i e s)
Re peat num b er of a x l e g r o u p s a s n e c e s s ar y DIMENSIONS IN METRES
FIGURE 9.2(B) 300LA RAIL TRAFFIC LOADS—AXLE GROUP SPACINGS
9.3 Light rail traffic design load
The light rail traffic design load shall be based on 150LA, derived by multiplying the 300LA rail traffic loads specified in Clause 9.2 by a factor of 0.5, with nine (9) axles. The nine axles shall comprise the simulated locomotive axle plus two groups of four trailing axles. For bridges where queuing of light rail vehicles is possible, additional trailing axle groups may be included, as specified by the relevant authority 9.4 Multiple track factor for rail bridges
When loading a number of tracks simultaneously, the multiple track factors given in Table 9.4 shall be used, as appropriate. The number of tracks loaded and the load patterning shall be selected to produce the most adverse effects in the member under consideration.
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AS 5100.2:2017
TABLE 9.4 MULTIPLE TRACK FACTORS Number of tracks loaded
Multiple track factor
1
1.00
2
1.00 for both tracks
3
1.00 for two tracks and 0.85 for the third track
4
1.00 for two tracks, 0.85 for the third track and 0.70 for the fourth track
5 or more
1.00 for two tracks, 0.85 for the third track, 0.70 for the fourth track and 0.60 for the remaining tracks
9.5 Dynamic load allowance 9.5.1 General
The dynamic load allowance (α) for rail traffic load effects shall be a proportion of the static rail traffic load, and shall be calculated by the methods specified in this Clause. It shall have the same value for all structural material types. The value of α shall depend on the characteristic length (Lα). Accessed by CENTRAL QUEENSLAND UNIVERSITY on 06 Jun 2017 (Document currency not guaranteed when printed)
The dynamic load allowance shall apply to both the ULS and SLS. The design action is equal to (1 + α) the load factor the action under consideration. In cases where a member acts in two different modes, e.g. as a deck support and also as part of the main girder, the dynamic load allowance shall be calculated separately for the structural actions in each mode, and the actions summed. 9.5.2 Characteristic length (Lα)
For main girders and components of rail bridge superstructures, the characteristic length (Lα) for each component shall be dependent on the structural geometry. The values of Lα for superstructure elements shall be as given in Table 9.5.2. For abutments, Lα shall be the length of the supported span. For piers, Lα shall be the sum of the lengths of the loaded adjacent spans. For bearings, Lα shall be per Table 9.5.2 for the member support.
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TABLE 9.5.2 CHARACTERISTIC LENGTH (L ) Case No.
Characteristic length (L ) m
Bridge members, types of bridge
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Floor members 1
Stringers
Cross-girder spacing +3.0
2
End stringers
Cross-girder spacing
3
Cantilevered stringers
0.5
4
Cross-girders, including cantilevered crossgirders, loaded by simply supported stringers and Twice the cross-girder spacing +3.0 continuous deck elements
5
End cross-girders, including cantilevered end cross-girders
6
Deck slabs between supports
Span of the main girders or twice the span of the deck slab, whichever is less
7
Cantilevered deck slabs
Span of the main girders or twice the distance between each support, whichever is less
8
Suspension bars or supports loaded by crossgirders only
The values to be used shall correspond to those applying to the cross-girder, as given in Cases 4 and 5
4.0
Main girders 9 10
Simply supported main girders
Span of main girders
Continuous main girders over n spans where—
for—
L m = 1/n (L 1 + L 2 ……+L n )
n
=
2
3
4
5
x
=
1.2
1.3
1.4
1.5
L = xL m , but L max. 11
Cantilever portions of cantilever bridges
Length of the cantilevered portion plus the span of any suspended girder supported by the cantilever
12
Suspended girders of suspended span bridges
Span of the suspended girder
13
Arches
Half span
14
Buried structures (e.g. pipes, culverts, buried arches)
Half span
15
Plate web girders at bottom of welded stiffeners
0.5
16
Truss members: (a)
17
Top and bottom chords
Three times the length from adjacent panel points
(b)
Verticals
Three times the length between chords
(c)
Diagonals not intersected by members complying with this Standard
Three times the horizontal or vertical projection, whichever is the shorter
(d)
Diagonals intersected by members complying with this Standard
Six times the horizontal or vertical projection of the overall length, whichever is the shorter
Lattice girder members: (a)
Top and bottom flanges and webs
As for main girders
(b)
Lattice members
Six times the horizontal or vertical projection of the overall length from web to web, whichever is the shorter (continued)
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AS 5100.2:2017
TABLE 9.5.2 (continued) Case No.
Characteristic length (L ) m
Bridge members, types of bridge
18
Bracing members: (a)
Horizontal or vertical members parallel to or perpendicular to the track
Three times the member length
(b)
Diagonal members with respect to Item (a), if not intersected by members complying with this Standard
Three times the projected length horizontally or vertically, parallel to or perpendicular to the track, whichever is the shorter
(c)
Diagonal members, with respect to Item (a), if intersected by members complying with this Standard
Six times the projected overall length horizontally or vertically, parallel to or perpendicular to the track, whichever is the shorter
LEGEND: n = L1, L2, Ln = x = = Lm L max. = = L
number of continuous main girder spans span lengths of a continuous structure, in metres coefficient (Case 10) average span length (Case 10) largest of the spans L 1 , L 2 , L n , in metres characteristic length
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9.5.3 Dynamic load allowance for bending effects
The value of the dynamic load allowance (α) for bending moment for ballasted deck spans, open deck spans or spans with direct rail fixation spans shall be calculated as follows:
2.16 0.27 0.67 = 0.2 0.5 Lα 0.20
L
= characteristic length in metres
. . . 9.5.3
where The value of for steam locomotives shall be increased by 20%. Transoms for open deck bridges and local effects for direct fixed tracks shall be designed with a dynamic load allowance of 1.0. Where a transition approach to a bridge abutment is not provided, α shall be increased by not less than 50% of the calculated dynamic load allowance unless otherwise approved by the relevant authority. 9.5.4 Application
For all parts of the structure extending down to the ground level, the dynamic load allowance (α) shall be as specified in Clause 9.5.3. For all parts of the structure below ground, culverts and soil steel structures below the ground level, α shall be linearly transitioned from the ground level value to zero (0) at a cover depth of 2 m. For structures in embankments, the ground level shall be taken as the underside of the ballast. The dynamic load allowance established for the appropriate cover depth shall apply to the entire structure. The depth of the cover shall be measured from the underside of the ballast. 9.5.5 Dynamic load allowance for other load effects
The dynamic load allowance (α) for shear, torsion and reactions shall be taken as 0.67 of the value for bending moment. Where the application of the dynamic load allowance leads to greater safety or stability, e.g. against overturning, α shall be taken as zero (0). www.standards.org.au
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Where deflections are to be calculated for serviceability loads, including dynamic load allowance, 0.67 of the dynamic load allowance () shall be used. Where a transition approach to a bridge abutment is not provided, α shall be increased by not less than 50% of the calculated dynamic load allowance unless otherwise approved by the relevant authority. 9.5.6 Dynamic load reversal
Consideration shall be given to the reversal of the dynamic response to live load. (Vibrations may continue and slowly decay after passing of traffic.) In particular, the minimum reaction on bearings shall allow for the reduction, which may occur from the results of the dynamic effects. 9.6 Distribution of rail traffic load 9.6.1 General
The distribution of rail traffic load to the supporting members shall be calculated using a rigorous analysis in accordance with the appropriate clauses of the relevant material Part of the AS(AS/NZS) 5100 series.
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In the absence of a rigorous analysis, rail traffic loads shall be deemed to be distributed as set out in Clauses 9.6.2 to 9.6.5, as appropriate. 9.6.2 Open deck steel rail bridges
Timber bridge transoms shall be designed on the assumption that the maximum wheel load on each rail shall be distributed equally to all transoms or fractions thereof within a length of 1.2 m, but shall be not greater than three transoms. For the design of beams, the rail traffic load shall be distributed and shall be applied via the transoms as above. In such cases, additional longitudinal distribution of such loads shall not be assumed. 9.6.3 Ballasted deck steel rail bridges
Provided that sleepers are spaced at no more than 700 mm centres, and not less than 150 mm of ballast is provided under them, the load from each axle may be uniformly distributed longitudinally over a length of 1.1 m, and uniformly distributed laterally over a width equal to the length of the sleeper plus the minimum distance from the bottom of sleeper to the top of the beams. This width shall be not greater than 4.0 m, the distance between track centres of multiple track bridges, or the width of the deck between ballast retainers. 9.6.4 Ballasted deck concrete rail bridges
Rail traffic loads on ballasted deck concrete bridges shall be uniformly distributed longitudinally over a length of 1.1 m, plus the depth of ballast under the sleeper, plus twice the effective depth of slab. The total length shall be not greater than the axle spacing. The loads shall be uniformly distributed laterally over a width equal to the length of the sleepers plus the depth of ballast below the bottom of the sleepers, plus twice the effective depth of the concrete slab, unless limited by the extent of the structure. This width shall not be greater than the distance between centres of adjacent tracks on multiple track bridges. 9.6.5 Direct fixation
The distribution of rail wheel loads through directly fixed track shall be determined on the basis of the relative stiffness of the rail, the rail fixing supports and the superstructure.
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AS 5100.2:2017
9.7 Horizontal forces 9.7.1 Centrifugal forces
For rail bridges on horizontal curves, allowance shall be made for the centrifugal effects of rail traffic load by applying a centrifugal force (Fc) corresponding to each axle load horizontally through a point 2 m above the top of the rail. The horizontal centrifugal force resulting from rail traffic loads shall be proportional to the design rail traffic load, and for each axle, Fc (in kilonewtons) shall be calculated as follows: Fc
V 2A rg
. . . 9.7.1
where V = design speed, in metres per second A = axle load, in kilonewtons r = radius of curve, in metres g = acceleration due to gravity (9.81 m/s2)
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The specified centrifugal force shall not be increased by the dynamic load allowance. Centrifugal and nosing forces due to rail traffic load shall not be applied simultaneously. 9.7.2 Braking and traction forces 9.7.2.1 General
Rail bridges of all deck types shall be designed for loads arising from longitudinal braking and traction forces in combination with their coexisting rail traffic loads. These forces shall be applied to the top of rail and be determined using one of the following methods: (a)
The empirical method.
(b)
The rational method.
The empirical method requires that occupied tracks be loaded for the full length of the bridge. The rational method permits partial loading of tracks. Where account is to be taken of tracks that are subject to variable and/or partial rail vehicle loadings, the rational method shall be used as approved by the relevant rail authorities. Braking and traction forces for a 300LA rail vehicle shall be taken to act at heights of 2.0 m and 0.9 m respectively above top of rail. For specific rail vehicles, these heights shall be derived from data supplied by their manufacturers if required. Traction forces shall be assumed to be applied uniformly through the axles of driver cars or locomotives, as applicable, whilst braking forces shall be assumed to be applied uniformly through all axles, unless otherwise directed by the relevant rail authorities. Dynamic load allowances shall not be applied to braking and tractions forces derived from either of the above methods. For bridges that carry both rail traffic and road traffic, the relevant rail and road authorities shall be consulted. 9.7.2.2 Empirical method
For a 300LA rail vehicle, the longitudinal forces per track applied to a bridge shall be calculated as follows: (a)
Braking forces: BF
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= 200 + 15LLF
. . . 9.7.2.2(1) Standards Australia
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where
(b)
BF
= longitudinal braking force, in kilonewtons
LLF
= total length of the bridge, in metres
Traction forces: for
LLF 25 m
. . . 9.7.2.2(2)
825 + 15 (LLF 25)
for
25 m < LLF 50 m
. . . 9.7.2.2(3)
1200 + 7.5 (LLF 50)
for
50 m < LLF 250 m
. . . 9.7.2.2(4)
= 200 + 25LLF
TF
2700 + 5.0 (LLF 250) for
250 m < LLF
. . . 9.7.2.2(5)
where TF
= longitudinal traction force, in kilonewtons
LLF
= total length of the bridge, in metres
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For specific rail traffic loads, the above braking and traction forces shall be multiplied by a factor equal to the equivalent line load intensity (in kilonewtons per metre) of the specific rail traffic load divided by the 300LA line load intensity of 100 kN/m. For a 150LA light rail vehicle, this factor shall be taken as 0.5. For multiple track bridges, the above longitudinal rail forces shall be multiplied by the appropriate multiple coexistence factors from Table 9.7.2.2 when used in combination to produce the most adverse effect. TABLE 9.7.2.2 BRAKING AND TRACTION FORCES MULTIPLE COEXISTENCE FACTORS Number of rail vehicles
Multiple coexistence factor
1
1.00
2
1.00 for both rail vehicles
3
1.00 for two rail vehicles and 0.5 for the third rail vehicle
4 or more
1.00 for two rail vehicles, 0.5 for the third rail vehicle and 0.25 for the remaining rail vehicles
9.7.2.3 Rational method
The relevant rail authorities shall stipulate the bridge-specific design parameters to be used in applying the rational method, which shall include, but not be limited to, the following data: (a)
Rail vehicle specifications, including the following where applicable: (i)
Critical rail vehicle dimensions.
(ii)
Rail vehicle tare and passenger loads.
(iii) Rail vehicle traction characteristics. (iv)
Rail vehicle braking characteristics.
(b)
Minimum clear longitudinal distances between consecutive rail vehicles on the same track.
(c)
Guidelines for multiple rail vehicle combinations.
For the purposes of this Clause, a rail vehicle is defined as a single train comprising— (i)
driver cars and trailer cars for an electric passenger train; or
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(ii)
AS 5100.2:2017
locomotives and carriages for a diesel passenger train; or
(iii) locomotives and wagons for a diesel freight train; or (iv)
special rail vehicle consist, such as a heritage train.
A bridge shall be analysed using the above parameters so as to produce the most adverse effect. Where this requires a bridge to be loaded simultaneously with a number of rail vehicles, the forces produced by each of these rail vehicles shall be multiplied by their respective multiple coexistence factors derived from Table 9.7.2 when combined with the effects from the other rail vehicles that are also present on the bridge. 9.7.2.4 Distribution of forces
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The distribution of the longitudinal forces derived in Clauses 9.7.2.2 and 9.7.2.3 through a bridge structure shall be computed using a valid rail-structure interaction model approved by the relevant rail authorities. This model shall take account of all relevant factors, such as the following, where applicable: (a)
Bridge-specific rail vehicle design parameters.
(b)
Track and bridge alignment.
(c)
Continuity/jointing of rails, including rail load transfer devices.
(d)
Stiffnesses of rails, turnouts, crossovers and the like.
(e)
Stiffnesses of ballast and transoms.
(f)
Longitudinal deformation characteristics of rail fixings.
(g)
Longitudinal shear stiffnesses of bridge bearings.
(h)
Longitudinal articulation of bridge superstructures.
(i)
Longitudinal stiffnesses of bridge piers and abutments, including their foundations.
(j)
Differential temperatures between rail and bridge,
(k)
Shrinkage and creep of concrete superstructures.
(l)
For the empirical method, modelling of the trackform for the extent of the bridge deck only. For the rational method, modelling of the trackform and the appropriate rail vehicle loadings for 100 m minimum beyond each bridge abutment.
9.7.3 Nosing loads
Rail bridges that are intended to carry 300LA rail traffic loads shall be designed to resist a lateral nosing load of 100 kN applied at top of rail level in either direction and at any point along the structure. For light rail, the nosing load shall be the value for 300LA loading multiplied by a factor of 0.5. For rail loads other than 300LA, this load shall be adjusted by the ratio of the maximum axle load in the specified design traffic load to the 300 kN load. Nosing loads— (a)
shall not be increased by the dynamic load allowance; and
(b)
shall not be reduced at low speeds. NOTE: Nosing loads are independent from the speed.
Centrifugal and nosing forces due to rail traffic load shall not be applied simultaneously. 9.7.4 Loads on ballast kerbs
For ballasted rail bridges with kerbs required to retain the ballast and the effects of transverse horizontal loads from rail traffic, the loads shall include ballast pressure and the effects of centrifugal force and nosing load.
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The horizontal load from an individual axle shall be distributed longitudinally along the face of the kerb over a length of 1 m plus twice the distance from facing end of sleeper to the inner face of the kerb. The load shall be applied at the top of sleeper level. 9.8 Fatigue load 9.8.1 Fatigue design traffic load
The fatigue design traffic load for rail bridges shall be the design rail traffic load and half of the design dynamic load allowance. The distance between the centres of the axle groups (Lv) shall be varied between 12 m and 20 m to produce the maximum fatigue design stress range ( f * ) (see Clause 9.8.2). 9.8.2 Fatigue design stress range ( f * )
The fatigue design stress range ( f * ) in any element of a bridge structure, shall be derived from the passage of the fatigue design traffic load over the bridge. It shall be the algebraic difference between the maximum and minimum stresses caused by that load. NOTE: Stresses and stress ranges caused by other load effects need not be included.
9.8.3 Effective number of stress cycles (n)
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The effective number of stress cycles (n) of the fatigue design stress range ( f * ) to be considered in the design of the structure shall be calculated as follows: n = CTnT
. . . 9.8.3
where CT = base number of load cycles for the track category, as given in Table 9.8.4 nT = number of equivalent stress cycles of amplitude f * per train, which depends on Lf and Lv, as given in Table 9.8.3 Lf = span of main girders, trusses or stringers; or cross-girder spacing for cross-girders Lv = distance between the centres of axle groups (i.e. the length of the vehicle) TABLE 9.8.3 VALUES OF nT Lf
nT
< 2.5
240
2.5 < L f < 9.0
60.0
9.0 < L f < 25.0
2 L v Lf + 2 60 Lf Max . 60 Min . 2
> 25.0
2.0
3
9.8.4 Track category for fatigue load
The base number of load cycles (C T) for fatigue load depends on the track category. It shall be not less than the values given in Table 9.8.4 unless otherwise approved by the relevant authority.
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AS 5100.2:2017
TABLE 9.8.4 VALUES OF CT Track category
CT
Heavy haul freight
6 10 5
All passenger and light rail lines
1 10 5
Main line freight
1 10 5
Branch line freight
1 10 4
9.8.5 Multiple track bridges
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For elements of multiple track rail bridges that are subject to loads from more than one track, the fatigue loads, both the fatigue design traffic load specified in Clause 9.8.1 and the fatigue design stress range specified in Clause 9.8.2, shall be determined from the full fatigue design traffic load on one track, and a load on the other track(s) of 80% of their full fatigue design traffic load with no dynamic load allowance. NOTE: The fatigue calculations for multiple track bridges may also be carried out by estimating the number of load events in the life of the element in which two or more trains will be loading the element under consideration at any one time. If the effect of the load from multiple tracks results in a stress range more severe than that due to a single track, a cumulative damage calculation for the cases of single-track and multiple-track loads should be performed.
9.9 Load factors
For ULS, SLS and fatigue limit state design loads, the load factors for the design rail traffic load shall be as given in Table 9.9(A). The load factors to be applied in calculating centrifugal, nosing and longitudinal forces shall be as given in Table 9.9(B). Each of the design horizontal forces due to rail load shall be applied simultaneously with the vertical rail load and such load cases shall be considered a single load, as specified in Clause 23.1.4. Centrifugal forces and nosing loads shall not be applied simultaneously. TABLE 9.9(A) LOAD FACTORS FOR DESIGN RAIL TRAFFIC LOAD ( Q) Load 300LA rail traffic load
Limit state Ultimate
Serviceability
Fatigue
1.6
1.0
1.0
TABLE 9.9(B) LOAD FACTORS FOR DESIGN RAIL HORIZONTAL LOADS Traffic load
Limit state Ultimate
Serviceability
Fatigue
Centrifugal forces
1.6
1.0
N/A
Nosing and kerb forces
1.6
1.0
N/A
Longitudinal braking and traction forces
1.6
1.0
N/A
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9.10 Deflection limits
The deflection limits of a rail bridge under traffic for SLS shall be appropriate to the structure and its intended use, the nature of the loading and the elements supported by it. Notwithstanding this requirement, the deflection of rail bridges for SLS under traffic load plus dynamic load allowance shall be not greater than 1/640 of the span and 1/320 of the cantilever projection. NOTE: In order not to detract from their appearance, bridges should be designed so that their hog does not exceed 1/300 of the span and they do not sag under permanent loads.
Rail bridges shall not deflect so that they uncouple rail traffic carriages or wagons nor they infringe clearance diagrams. Rail bridge superstructures with open deck or directly fixed track and span lengths greater than 20 m shall be cambered. The camber shall be determined such that the rail track shall be at its theoretical level under the effects of the permanently applied loads; for example, dead load, superimposed dead load, long-term prestressing, shrinkage and creep effects where applicable, and half of the design rail traffic loads, excluding dynamic load allowance.
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10 MINIMUM RESTRAINT LOAD
To ensure that the superstructure has sufficient lateral restraint to resist lateral forces not otherwise accounted for in the design, a positive lateral restraint system between the superstructure and the substructure shall be provided at piers and abutments. For continuous superstructures, lateral restraints may be omitted at some piers, provided each continuous section of the superstructure is adequately restrained. The restraint system for each continuous section of the superstructure shall be capable of resisting an ultimate design horizontal force normal to the bridge centre-line of 500 kN or 5% of the superstructure dead load at that support, whichever is greater. Supports providing this lateral restraint shall also be designed to resist this design force. A load factor 1.0 shall be used. The 500 kN horizontal force may, subject to authority approval, be reduced to 200 kN or 5% of the superstructure dead load for pedestrian bridges crossing low flood velocity creeks or gullies. Restraints shall have sufficient lateral clearance to allow thermal movements, especially on wide and curved superstructures. If the transverse load requirement specified in other parts of the AS(AS/NZS) 5100 series is greater than the requirements of this Clause, the restraints shall be deemed to satisfy the requirements of this Clause. NOTE: Friction is not considered a positive restraint.
Except for bridges crossing low flood velocity creeks or gullies, and where there is uplift at a bearing or support point under a combination of 500 kN acting upwards on the superstructure and the ultimate minimum permanent vertical load, a positive vertical restraint shall be provided to resist the uplift force. 11 COLLISION LOADS 11.1 General
Collision protection shall be considered in accordance with AS 5100.1. Collision loads shall be considered at the ULS with a load factor of 1.0. The collision loads shall be as specified in Clauses 11.2 to 11.6 and load combinations in accordance with Clause 23, where applicable.
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AS 5100.2:2017
Where an alternative load path is to be provided for road bridges in accordance with AS 5100.1 Clause 15.3.3, the superstructure shall be designed with sufficient redundancy to be capable of supporting the dead load plus a minimum 20% of the design traffic load (gG + gsGgs + 0.2QQ) at the ULS with one or more piers or columns removed. The number of supports to be removed and the traffic load for the redundancy action shall be determined by a risk analysis approved by all relevant authorities. 11.2 Collision load from road traffic
For the purpose of this Clause, support elements are piers, columns, abutments and walls that provide vertical supports to overhead structures. It also includes support elements for developments adjacent to or over a roadway. The supports for a bridge or other structure as specified above, that is within the clear zone, as defined by Austroads Guide to Road Design (Part 3), shall be designed to resist a minimum equivalent static load of 2700 kN acting in any direction in a horizontal plane. The load shall be applied 1.2 m above ground level. This load shall be considered at the ULS. A load factor of 1.0 shall be used for the ULS.
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NOTE: This load does not represent a head-on collision. Head-on collision loads can be significantly higher and are outside of the scope of this Standard.
11.3 Loads on protection beams
Where specified by the relevant authority, protection beams shall be installed to protect the superstructure of low clearance bridges from impact from road vehicles. They shall be designed for the ultimate loads given in Table 11.3, with a load factor of 1.0. Protection beam supports shall be capable of resisting loads 25% greater than the capacity of the protection beam itself. TABLE 11.3 ULTIMATE LOADS ON PROTECTION BEAMS ULS kN
Load Horizontal
1000 (towards the bridge) 750 (away from the bridge)
Vertical (uplift)
500
11.4 Collision load from rail traffic 11.4.1 General
This Clause applies to all structures above and within 20 m adjacent to rail tracks, such as— (a)
rail bridges;
(b)
road bridges;
(c)
pedestrian, cyclist path and maintenance bridges;
(d)
deflection walls and crash walls;
(e)
air space developments;
(f)
external developments; and
(g)
similar structures in underground railways.
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This Clause does not apply to— (i)
structures that only support signals, overhead wiring, lighting or communications equipment;
(ii)
gang sheds adjacent to tracks;
(iii) waiting rooms and ticket offices on platforms. In addition to the design requirements specified herein, any other design requirements of the relevant rail authority shall be satisfied. A load factor of 1.0 shall be used for the ULS. The loads mentioned herein shall not be reduced when the design rail traffic load is less than 300LA. For light rail, all collision loads shall be the same as for 300LA loads. 11.4.2 Collision loads on support elements
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11.4.2.1 General
For the purpose of this Clause, support elements are piers, columns, abutments and walls that provide vertical supports to overhead and adjacent structures. They also include deflection and crash walls to protect bridges and support elements for developments adjacent to or over a rail line. 11.4.2.2 Frangible pier
The design loads for a frangible pier shall be determined from a risk assessment undertaken in accordance with AS 5100.1 Clause 13.3.2. 11.4.2.3 Support within 10 m of track centre-line
Unless otherwise specified by the rail authority, supports located within 10 m of the centreline of the rail track, which do not comply with the redundancy requirements of AS 5100.1, shall be designed to resist the following minimum collision loads, applied simultaneously: (a)
4000 kN parallel to rails.
(b)
1500 kN normal to rails.
The loads specified in Items (a) and (b) shall be applied horizontally at 2 m above rail level distributed over a length of 2.0 m by 0.5 m. NOTE: These loads do not represent a head-on collision. Head-on collision loads can be significantly higher and are outside of the scope of this Standard.
11.4.2.4 Support elements located between 10 m and 20 m from track centre-line.
Where supports are located between 10 m and 20 m from the centre-line of the rail track, a risk analysis shall be carried out and approved by the relevant rail authority, which shall determine the required level of protection. If the level of redundancy does not meet the redundancy requirements of AS 5100.1, support elements shall be designed to resist a collision load of 1500 kN, acting at any angle in the horizontal plane directed towards the support from the adjacent track centre-line, applied at 2 m above the ground level adjacent to the support. NOTE: Some rail authorities permit relaxation of this loading where platforms, under certain conditions, provide protection to the columns.
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AS 5100.2:2017
11.4.3 Bridge and structural components within 10 m of the centre-line of the rail track
Any part of any structure specified in Clause 11.4.1, including the superstructure, within 10 m horizontally and 5 m vertically of the centre-line of the nearest rail track, shall be designed to resist a minimum collision load of 500 kN. The collision load shall be applied in any direction and at any height, directed towards the component from the adjacent track centre-line, except downwards. Above 5 m and up to 10 m vertically above the rail track level, this collision load shall vary linearly from 500 kN at 5 m to zero at 10 m. When applied vertically upwards, the force shall be distributed over an area of one square metre, to allow for roof crushing of the rail vehicle. Platforms shall not be assumed to provide protection to permit reduction of this collision load. This collision load shall not be applied in conjunction with the loads specified in Clause 11.4.2. For underground rail and air space developments, these loads shall be multiplied by a factor of three (3) and there shall be no reduction for vertical height up to 10 m. When applied vertically upwards, this collision load shall be distributed over an area of 2 m2. 11.4.4 Through-type rail bridge superstructures Accessed by CENTRAL QUEENSLAND UNIVERSITY on 06 Jun 2017 (Document currency not guaranteed when printed)
11.4.4.1 General
This Clause (11.4.4) applies to the principal structural elements of through-type superstructures that extend vertically above the level of the rail track that they are supporting. This includes through-girders (flanges and webs), through trusses (top chord, verticals and diagonals) and through-arches (arch chords and hangers). These elements are usually in close proximity to the rail line. 11.4.4.2 Collision loads within the bridge
Unless otherwise approved by the rail authority, the bridge shall be designed for collision loads from a derailed train anywhere within the bridge. A barrier extending not less than 2.0 m above rail, or to the top of the uppermost primary structural element, whichever is the lower, shall be provided unless the bridge superstructure is designed to resist the collision load defined in Clause 11.4.3 and there is no possibility of a vehicle snagging (that is, if the primary structural elements provide a smooth and solid impact surface). The barrier shall be designed to resist the collision load defined in Clause 11.4.3 and shall provide a smooth and solid impact surface such that there is no possibility of a vehicle snagging. Primary structural elements higher than 2.0 m above the rail tracks shall be designed for the collision load defined in Clause 11.4.3. Alternatively, the collision load to be resisted by the primary structural elements and/or the barrier may be determined from a dynamic collision analysis, approved by the relevant authority, which takes into consideration design track speed and geometry, design load with representative rolling stock characteristics (centre of mass and distribution, stiffness of components, etc.), bridge and barrier stiffnesses. 11.4.4.3 Protection against head-on collision with the end of the through-girder, arch or truss
Unless otherwise approved by the rail authority, the ends of the girder, arch or truss shall be protected against head-on collision as specified in this Clause.
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A deflection wall or barrier shall be provided in front of the end of the girder, arch or truss, to protect it from head-on collision. This barrier may be an independent concrete wall or integral with the approach slab, or a steel post and rail barrier and shall be designed in accordance with Clause 11.4.4.2. 11.5 Derailment loads 11.5.1 General
Rail bridges designed to carry 300LA loads shall be designed for two separate train derailment load cases as set out in Clauses 11.5.2 and 11.5.3. The loads shall be proportioned if a different traffic load is specified. Derailment loads shall only be considered for the ULS without dynamic load allowance, and shall act in combination with long-term permanent effects. 11.5.2 Derailment load Case A
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For derailment load Case A, a bridge shall be designed for the more unfavourable of the following loads: (a)
300LA load applied as wheel loads, separated by the track gauge, parallel to the track, and in the most unfavourable position within a distance to track centre-line (Lg), where Lg is equal to 1.5 times the track gauge.
(b)
A single vertical point load of 200 kN, acting at the most unfavourable position on any part of the structure.
For the loads specified in Items (a) and (b), an ultimate load factor of 1.2 shall be used. 11.5.3 Derailment load Case B
For derailment load Case B, a bridge shall be designed for an equivalent line load of 100 kN/m, over a length of up to 20 m, acting on the edge of the superstructure, using an ultimate load factor of 1.0. 11.5.4 Derailment kerbs
Where the relevant authority requires a kerb to be provided to keep derailed bogies tracking parallel to and in close proximity to the rails, the following provisions shall apply: (a)
The kerb height shall extend 200 mm above the height of the adjacent running rail. Kerbs shall be located as close as practicable to the adjacent running rail.
(b)
The kerb shall extend to the full length of the bridge, including approach transition slabs, without snagging points.
(c)
Kerbs shall be designed for a horizontal load of 300 kN distributed over a 1 m length, acting at the top of the kerb, perpendicular to the centre-line of the track.
(d)
An ultimate load factor of 1.0 shall be used.
11.6 Collision from waterway traffic
The harbour master, port authority or other relevant authority shall recommend the type of vessel, weight of vessel and speed of impact on the bridge. This includes the channel and adjacent pier locations. The upper bound loads shall consider all vessels currently operating in the waterway or likely to operate in the waterway for the next 100 years. The minimum velocity of impact shall be the larger of the maximum flood velocity or the maximum speed of the vessel under power. The proposed design vessel and speed shall be reviewed and approved by the relevant authority.
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Unless a more advanced method of analysis is adopted, or unless otherwise specified by the relevant authority, the ultimate equivalent static vessel impact force shall be determined in accordance with AASHTO LRFD Bridge Design Specifications. The resulting minimum equivalent static ship impact force applicable to piers in navigable waterways shall be approved by the relevant authority. Piers in the waterway shall be designed for an equivalent static vessel impact force in the direction of the channel centre-line. The piers shall be designed to resist a load of 50% of the equivalent static vessel impact force applied separately in a direction perpendicular to the channel centre-line. These forces shall be applied anywhere between 1.0 m above mean low water spring (MLWS) and 1.0 m above mean high water spring (MHWS). The superstructure shall be designed to resist a horizontal force equal to 20% of the equivalent static vessel impact force applied independently of impact loads to the piers. 12 KERB AND BARRIER DESIGN LOADS AND OTHER REQUIREMENTS FOR ROAD TRAFFIC BRIDGES 12.1 Kerb design loads
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Kerbs shall be designed to resist an ultimate design load of 15 kN/m applied laterally at the top of the kerb. 12.2 Barriers 12.2.1 General
The design criteria, including loads and geometric requirements provided in this Clause (12) and in AS 5100.1 shall be used for the following: (a)
Developing a prototype barrier for a crash test program to validate vehicle/barrier interaction performance.
(b)
Designing minor modifications to a barrier system that has been validated by either crash testing or performance review to develop a geometrically and structurally equivalent barrier. The modified barrier shall not have features that are absent in the validated configuration (which might detract from the performance of the barrier system).
(c)
Designing a modified barrier system to ensure that the components are capable of safely redirecting all vehicles nominated in the crash test vehicle criteria for that barrier performance level, as specified in AS 5100.1.
In order to minimize damage to bridge decks and for safety considerations, bridge barriers shall be designed as progressive strength systems in which barriers and then their connections fail prior to the failure of the supporting elements. 12.2.2 Traffic barrier design loads
The ultimate design loads and load distribution lengths for low, regular and medium traffic barrier performance levels, as defined in AS 5100.1, shall be as given in Table 12.2.2. The ultimate design loads and load distribution lengths for special barrier performance levels shall be the subject of specific investigations consistent with the criteria specified in AS 5100.1, and shall be specified by the relevant authority. NOTE: Typical design loads for special performance level barriers are given in Appendix A.
An ultimate load factor of 1.0 shall apply to the design of bridge barriers. The following load combinations shall be considered: (a)
Transverse and longitudinal loads applied simultaneously.
(b)
Vertical loads only.
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Concrete barriers are rigid barriers whilst post and rail barriers are semi-rigid. Where the barrier height is increased due to rail electrification, anti-throw or for protection requirements, the additional barrier height shall not be modelled in the design of the barrier system, as it is not required for vehicle redirection. All posts on a post and rail barrier shall have the same cross-section. All loads on rail and post-type barriers shall be applied for the greater effect of— (i)
equal load on each rail; and
(ii)
the centroid of the loads that is greater than or equals the minimum effective height in Table 12.2.3.
NOTE: A design methodology for barriers is provided in AASHTO LRFD Bridge Design Specifications.
The distribution of the longitudinal load to post shall be consistent with the continuity of rail elements. TABLE 12.2.2
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TRAFFIC BARRIER DESIGN LOAD AND CONTACT LENGTH Ultimate transverse Barrier performance outward load (F T ) level
Vehicle contact Ultimate length for longitudinal or transverse load transverse (L T ) and inward load longitudinal load (F L ) (L L )
Ultimate vertical downward load (F V )
Vehicle contact length MASH test for vertical level load (L V )
kN
kN
m
kN
m
Low
150
50
1.1
22
5.5
TL2
Regular
300
100
1.2
100
6
TL4
Medium
600
200
2.4
300
12
TL5
NOTES: 1
The design of a barrier system using this Table shall include a detailed analysis, such as a yield line analysis for a concrete barrier or an inelastic plastic moment analysis for a steel post and rail barrier.
2
The loads given in this Table shall be applied uniformly over the relevant specified contact lengths.
12.2.3 Effective height
The effective height of a barrier is defined as the height as measured from the reference surface of the resultant of the lateral resistance forces of the individual components of the barrier. Traffic barriers shall have sufficient height to ensure that the minimum effective height as given in Table 12.2.3 is achieved. The minimum effective height for the special performance levels shall be the subject of specific investigation consistent with the criteria specified in AS 5100.1, and shall be specified by the relevant authority. NOTE: Typical minimum effective heights for special performance level barriers are given in Appendix A.
For low performance level concrete, metal or combined concrete and metal barriers with a vertical face, the minimum actual height shall be 700 mm unless prototype testing indicates that a lower height system fulfils the requirements of the AASHTO Manual for Assessing Safety Hardware (MASH).
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TABLE 12.2.3 MINIMUM EFFECTIVE HEIGHT OF TRAFFIC BARRIER Barrier performance level
Minimum effective height mm
Low
600
Regular
900
Medium
1200
12.2.4 Connection
The yield strength of steel anchor bolts for the barrier shall be fully developed by bond, hooks, attachment to embedded plates or any combination thereof. Other means of connection shall be subject to approval of the relevant authority. A load factor of 1.05 shall apply to the design of connection bolts and connection reinforcement. 12.2.5 Continuity
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Full lateral strength shall be provided throughout the barrier length. In the case of steel railing, splices may be provided by bolted sleeve joints or full penetration butt welds. For bending and shear, full rail continuity shall be provided in the splice section. For tension, a minimum of 75% of the tensile strength of the theoretical gross rail section shall be provided in the splice section. 12.3 Bridge deck
The loads transmitted to the bridge deck shall be determined from the results of load testing or ultimate strength analysis of the barrier system using the loads given in Table 12.2.2. The design ultimate capacity of the bridge deck shall be a minimum of 1.1 times greater than the design ultimate capacity of the barrier connection to the deck. NOTE: The barrier impact loads and traffic loads on the deck need not be applied simultaneously when designing the deck.
12.4 Expansion joints and end barriers 12.4.1 Post and rail type barriers
Where the total longitudinal movement at rail level is 50 mm or less, joints providing continuity between lengths of rails or across expansion or rotational joints shall be capable of transmitting 75% of the tensile strength of the theoretical gross rail section. The joints shall be capable of transmitting the full design requirement of the rail in bending at any extension of the joint. Where the total longitudinal movement at rail level is greater than 50 mm, joints across expansion or rotational joints shall be capable of transmitting the full design requirement of the rail in bending and shear at any extension up to the full design movement at the joint plus 100 mm. Special end posts shall be provided at each side of the joint, spaced as closely together as required to compensate for the loss in beam action of the barrier over the joint. Where significant movements take place in a vertical or transverse horizontal direction, joints shall comply with this Clause. Where compliance is not possible, a discontinuity of the barrier is permitted. The gap between the ends of the rail shall be not greater than the calculated maximum joint gap plus 25 mm. NOTE: It is emphasized that this discontinuity is only permitted in extreme cases.
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Some form of bridging of the ends of the rails shall be devised to prevent a vehicle that is in contact with a deflected length of barrier directly striking the end of an undeflected length. When a bridging piece is used, it shall be securely attached to the end of the rail on the approach end. 12.4.2 Rigid barrier at a movement joint
Barrier panels on each side of a movement joint shall be designed in accordance with either of the following: (a)
They shall stand alone and shall not have any shear transfer arrangements incorporated across the joint. or
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(b)
They shall be continuous across a joint with a load transfer mechanism. The mechanism shall be proven by design or test and shall be subject to approval of the relevant authority. The load transfer mechanism shall be corrosion resistant and replaceable.
Where movements that produce a gap greater than 25 mm take place, a bridging plate shall be incorporated. The bridging plate shall be securely fixed to the approach traffic end, and shall be corrosion resistant and replaceable. Where the gap is greater than 600 mm, the bridging plate shall be designed to transfer the traffic barrier design loads to the adjacent end panels on each side of the joint. 12.5 Pedestrian and cyclist path barrier load
Pedestrian and cyclist path barriers shall be designed for the most extreme of the following loads: (a)
A load of 0.75 kN/m acting on the longitudinal rail or the top of the barrier simultaneously in a transverse and vertical direction.
(b)
A load of 1.0 kPa acting in a transverse direction on the total barrier infill area, whether comprising baluster, mesh or solid.
(c)
A single load of 0.6 kN acting over an area of 0.1 m 0.1 m in a transverse direction away from the path on the infill area, whether comprising baluster, mesh or solid,
(d)
Forces from wind load, water forces and debris or earthquake.
The deflection of a pedestrian or cyclist path barrier subject to the serviceability loading (a) to (c) above shall not exceed— (i)
for longitudinal members ............................................................................ L/800; and
(ii)
for posts ............................................................................................................ h/300, where L
= span of member between posts
h
= height of the post above the base plate
In addition to the provisions above, where the relevant authority specifies that the barrier is to restrain crowds or people under panic conditions, the barrier shall be designed for the most extreme of the following loads: (A)
A load of 3.0 kN/m acting in a transverse direction away from the path simultaneously with a vertical load of 0.75 kN/m acting on the top rail; or
(B)
A load of 1.5 kN/m acting in a transverse direction away from the path simultaneously with a vertical load of 0.75 kN/m on any one longitudinal member; or
(C)
A load of 1.5 kPa acting in a transverse direction away from the path on the total barrier infill area, whether comprising baluster, mesh or solid; or
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(D)
AS 5100.2:2017
A load of 1.0 kN acting over an area of 0.1 m 0.1 m in a transverse direction away from the path on the infill area
The load effects from barrier loading shall be considered in combination with the serviceability pedestrian loading. The load factors to be applied in calculating the pedestrian and cyclist path barrier loading shall be as given in Table 12.5. TABLE 12.5 LOAD FACTOR FOR DESIGN OF PEDESTRIAN AND CYCLIST PATH BARRIER LOAD Load Pedestrian and cyclist path barrier load
Limit state Ultimate
Serviceability
1.8
1.0
13 DYNAMIC BEHAVIOUR
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13.1 General
Vibration shall be considered at the SLS. NOTE: Vibration induced in bridges by traffic or pedestrians may cause alarm or public unease as to the safety of the structure or resonance in the structure.
13.2 Road bridges 13.2.1 With walkways
This Clause (13.2) shall apply to bridges and similar structures that support platforms or other areas intended for public use. The vibration of a road bridge shall be investigated as a SLS if the structure is fitted with a walkway intended for public use. The serviceability design load of 0.7 (M1600 moving traffic load without UDL), including dynamic load allowance, shall be positioned along the spans and within any design traffic lane to produce the maximum static deflection of the walkway. The deflection at the centre of the walkway shall be not greater than that shown in Figure 13.2.1, unless an investigation complying with Clause 13.2.3 is undertaken.
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STATIC DEFLECTIO N AT CENTRE OF WALK WAY, m m
Standards Australia
0
10
20
30
40
50
60
70
80
90
10 0
110
120
1
2
Ac c e pt a b l e
5
6
FIRST M O DE FLE XUR AL FREQ UEN CY, Hz
4
7
8
FIGURE 13.2.1 STATIC DEFLECTION LIMITS FOR ROAD BRIDGES WITH WALKWAYS
3
Unac c e pt a able ble
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9
10
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13.2.2 Without walkways
Where the deflection of a road bridge without a public walkway complies with the limits specified in Clause 7.11, the vibration behaviour of the bridge shall be deemed to be satisfied. 13.2.3 Detailed dynamic analysis
Where the deflection limits specified in Clause 7.11 and Clause 13.2.1 are exceeded, the vibration behaviour of the bridge shall be assessed by a rational method of analysis, using acceptance criteria appropriate to the structure and its intended use, as approved by the relevant authority. 13.3 Rail bridges
Where required by the relevant rail authority, vibration behaviour shall be assessed by a rational method of analysis using acceptance criteria appropriate to the structure and its intended use, as approved by the relevant authority. 13.4 Pedestrian and cyclist path bridges
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13.4.1 General
For pedestrian bridges with resonant frequencies for vertical vibration less than 5 Hz, the vibration of the superstructure shall be investigated as a SLS. Superstructures shall be proportioned such that, with one pedestrian traversing the structure, the maximum vertical acceleration shall be not greater than 0.25f00.78 m/s 2, where f0 is the fundamental frequency of vibration. The design pedestrian load shall have a weight of 700 N and be assumed to cross the structure at an average walking speed, in the range of 1.75 to 2.5 footfalls per second. This Clause (13.4) shall also apply to bridges and similar structures that support access routes to platforms or other areas intended for public use. NOTE: For determining the maximum vertical acceleration, see Clause 13.4.2.
Where the fundamental frequency of horizontal vibration is less than 1.5 Hz, special consideration shall be given to the possibility of excitation by pedestrians of lateral movements of unacceptable magnitude. NOTE: Bridges with low mass and damping, and expected to be used by crowds of people, are particularly susceptible to such vibrations. Specialist literature should be referred to.
13.4.2 Maximum vertical acceleration
In the absence of a more advanced analysis, and for simply supported bridges only, the maximum vertical acceleration (a), in m/s2, may be taken as: a
= 42f2y (m/s 2)
y
= static displacement due to design pedestrian load of 700 N, in metres
= dynamic response factor (see Figure 13.4.2)
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δ = 0.0 3 14.0
δ = 0.0 4
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DYNAMIC RESPO NSE FACTOR , Ψ
12.0
δ = 0.0 5
10.0
8.0
6.0
4.0
2.0
0
0
10
20
30
40
50
SPAN, m
NOTE: Values of for different types of construction are given in Table 13.4.2.
FIGURE 13.4.2 DYNAMIC RESPONSE FACTOR ( )
TABLE 13.4.2 LOGARITHMIC DECREMENT OF DECAY OF VIBRATION ( ) Bridge superstructure
Steel with asphalt or epoxy surfacing
0.03
Composite steel/concrete
0.04
13.5 Special structures
This Standard does not provide acceptance criteria for the dynamic behaviour of bridges with spans in excess of 100 m, or suspension and cable-stayed bridges. The dynamic behaviour of such structures under the action of traffic, wind or other loadings shall be the subject of special investigations. 14 EARTH PRESSURE FROM TRAFFIC LOADS 14.1 General
The load factors on earth pressure from traffic loads shall be determined in accordance with AS 5100.3.
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The surcharge shall not be increased by dynamic load allowance for the calculation of horizontal loads. 14.2 Surcharge loads from road traffic
Where highway traffic loads can approach within a distance equal to the effective height of the wall from the back face of the structure, an equivalent load caused by an additional height of fill, which diminishes over the height of the wall, as shown in Figure 14.2, shall be assumed for the purpose of calculating design earth pressure. This load shall be assumed to act above the finished grade and over the entire length of the retaining structure. The effect of foundations or other loads placed in or on the backfill, within a distance equal to the effective height of the wall, shall also be included. The surcharge shall be applied irrespective of whether or not there is provision for an approach slab in the bridge design.
Sur c har g e l oad in g : e q ui val e nt ad d i t i o n a l h e i g ht of f i l l (m) 0. 2 0.4 0.6 0.8 1.0 0
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2
4 D e pt h b e l ow to p of wall (m) 6
8
10
FIGURE 14.2 EQUIVALENT LOAD DUE TO ROAD TRAFFIC SURCHARGE
14.3 Surcharge loads from rail traffic
Where sleepers supporting rail traffic load are located within a distance from the back face of a retaining wall or abutment equal to the effective height of the retaining structure, an additional surcharge load equal to the rail traffic load shall be applied as a uniform load at the level of the underside of the sleepers as shown in Figure 14.3. An equivalent load caused by an additional height of fill shall be applied, or an alternative method of allowing for surcharge shall be used. In determining the distribution of rail traffic loads at the underside of sleepers, it is assumed that the total load for a given length of train shall be uniformly distributed over the area defined by the length of sleepers and the length of loaded track. The loaded track shall extend 0.55 m beyond the end axles of the length of train. The length of train shall be selected to produce the worst design effects. The resulting distributed loads shall be considered in the design as discrete areas of surcharge. These areas of surcharge shall be distributed with increasing depth below the underside of sleepers. The width of the distribution shall be increased in each direction at a slope of 1 horizontally to 2 vertically to determine the maximum vertical earth pressures at depth as a result of surcharge, as given in Table 14.3. In the transverse direction, the distribution width shall not exceed 4.5 m. www.standards.org.au
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When adjacent rail traffic load distributions overlap, the total load shall be considered to be uniformly distributed over the area defined by the outside limits of the individual rail load distributions at that depth. The total width of the distribution so determined shall not exceed the total width of the structure supporting the fill and, if the centroid of the load is not coincident with the loaded area, the load distribution shall be taken to vary linearly to satisfy statics. When determining lateral earth pressures on retaining walls and abutments, the width of the distribution shall be increased in each direction as specified above, and the vertical pressure calculated from that distribution shall be applied to any part of the retaining wall or abutment that is located within the zone of a 45° projection from the underside of the sleepers.
d/2 Ret aining wall
d/2
d/2 Ret aining wall
d/2
d/2
d/2
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2. 25 ma x. or to ret aining wall
2 . 25 m a x . Le n g t h of tr ac k c o n s i d er ed ere
C o m b i n e d area of sur c har g e if < 4. 5
Le n g t h of t r ac k c o n s i d er e d
Le n g t h of t r ac k c o n s i d er e d 2 . 25 m a x . d/2
LEGEN D: d = d e pt h b e l ow t h e un d er s i d e of s l e e p er s d/2 CASE 1 (At un d er s i d e of s l e e p er s)
CASE 2 (At a d e pt h d b e l ow u n d er s i d e of s l e e p er s)
d/2
CASE 3 (At a d e pt h d b e l ow u n d er s i d e of s l e e p er s t wo tr ac ks l oad e d)
DIMENSIONS IN METRES
FIGURE 14.3 SURCHARGE LOAD DISTRIBUTION FOR RAIL TRAFFIC
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TABLE 14.3 VALUES OF UNFACTORED VERTICAL PRESSURE vs. DEPTH BELOW 2.5 m LONG SLEEPER (300LA TRAIN LOAD) Distance from centreline of track (x), m x = 1.25
x = 0.0 abutment approach
Depth below sleeper (d) m
131
131
0.00
92
97
103
0.30
70
77
83
0.60
63
69
73
0.80
54
58
63
64
1.00
48
53
57
58
1.20
44
50
54
53
1.40
41
48
51
49
1.60
39
39
45
49
45
1.80
36
36
43
46
42
2.00
35
35
42
45
40
2.20
35
35
42
45
39
2.40
34
34
41
44
39
2.60
33
33
33
40
43
39
2.80
33
33
33
39
42
38
3.00
32
32
32
39
41
38
3.20
32
32
32
38
41
37
3.40
31
31
31
37
40
37
3.60
30
30
30
30
36
39
36
3.80
30
30
30
30
36
38
36
4.00
29
29
29
29
34
37
35
4.50
28
28
28
28
28
33
35
34
5.00
26
26
26
26
26
32
34
33
5.50
25
25
25
25
25
25
31
33
33
6.00
25
25
25
25
25
25
30
32
32
6.50
24
24
24
24
24
24
28
31
31
7.00
22
22
22
22
22
22
27
29
30
8.00
21
21
21
21
21
21
26
28
29
9.00
21
21
21
20
21
21
25
27
28
10.00
x = 7.0
x = 6.0
x = 5.0
x = 4.0
x = 3.0
x = 2.25
No vertical surcharge x x = 2. 25 1
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Line of 1 influence
d
Pre s sure distribution 1 2
4. 5 m
x = 1.5
NOTE: The values in the Table are based on the following assumptions: (a)
Values are for single track loading only.
(b)
Load distribution based on standard gauge concrete sleeper length 2.5 m.
(c)
Vertical pressure calculated assuming 1 to 2 longitudinal and transverse distribution, max width 4.5 m.
(d)
Calculated pressure assumed to be applied over a 1 to 1 distribution width.
(e)
x = 0 may be used for vertical pressure behind an abutment without an approach slab and no wing walls within 1 to 1 line of influence.
(f)
Intermediate values may be obtained by linear interpolation.
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15 EARTHQUAKE EFFECTS 15.1 General
Earthquake design shall be carried out using the force-based approach detailed in this Clause. NOTE: For design based on the displacement method, see Appendix B.
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The provisions for earthquake design in this Clause are applicable to bridges that include the following: (a)
Conventional superstructure and support types, such as slab, beam and slab, box-girder and truss bridges supported on single- or multi-column piers and/or abutments.
(b)
Spans not greater than 100 m.
(c)
Angular change of the direction of the longitudinal axis of the bridge between abutments less than 90°.
(d)
Skew angles less than 35°.
(e)
Maximum pier height of 30 m.
(f)
Maximum characteristic concrete compressive strength of 65 MPa in bridge substructures except that for bridge piers with characteristic concrete compressive strength higher than 65 MPa, design for earthquake load cases shall be carried out assuming characteristic concrete compressive strength of 65 MPa for the piers.
For other bridges, or for bridges where seismic base isolation is to be implemented, specialist advice shall be sought for the assessment of earthquake effects. The effects of excessive settlement of approach embankments and the increased earth pressure on abutments shall be considered in the design for earthquake effects. The possibility of soil liquefaction shall be investigated where saturated sandy and silty soils within 10 m of the ground surface have a standard penetration test (SPT) value of 10 or less. The earthquake effects calculated in accordance with this Clause shall be considered as design effects at the ULS for member strengths, overall stability of both the structure and its components, and horizontal movements. 15.2 Force-based principles 15.2.1 Analysis principles
The earthquake forces shall be calculated from the design action coefficient, which is the design seismic acceleration expressed as a fraction of gravitational acceleration. The design action coefficient depends on the bridge earthquake design category and design performance level, the probability factor, the hazard factor, the site subsoil class, and the fundamental natural period and design ductility of the structure. The bridge shall be subdivided longitudinally into bridge frames between expansion joints and abutments. For longitudinal earthquake response, each bridge frame shall be considered separately (stand-alone analysis) and the results shall be compared with a further analysis where all joints are considered to be fully closed. For transverse response, each bridge frame shall be considered separately, with the mass and stiffness of adjacent bridge frames modelled at the movement joint where the fundamental natural period of the adjacent bridge frame differs by more than 25% from that of the bridge frame under consideration.
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AS 5100.2:2017
Where analysis of vertical earthquake response is required by Clause 15.4, a span-by-span static analysis may be used, provided the span under consideration is modelled together with adjacent continuous spans, if any, at either end of the span. End support conditions at the far end of the adjacent span shall be considered fixed if continuous over the support or pinned as appropriate (e.g. if the end of the adjacent span is simply supported at an abutment). The fundamental natural period of vibration of each bridge frame in the longitudinal direction (i.e. span direction), the transverse direction and (where required) the vertical direction shall be determined using acceptable methods of structural analysis. The design actions shall be determined from the earthquake forces using acceptable methods of structural analysis. Reinforced concrete members shall be modelled using the effective cracked-section stiffness. Prestressed concrete members shall be modelled using the gross-section stiffness. The longitudinal and transverse stiffness of piers shall include the influence of foundation and bearing flexibility, where appropriate. 15.2.2 Seismic weight distribution
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The seismic weight is the mass multiplied by gravitational acceleration. As a minimum representation of the seismic weight distribution, the tributary superstructure weight (including weight of dead load and weight of superimposed dead load), pier headstock weight and tributary weight of pier columns shall be combined as a single weight acting in the plane of the pier, and at the resultant height of the combined weights. In this context, the tributary weight of the pier columns may be taken as 33% of the total pier column weight, positioned at the top of the pier column. For bridges with tall piers of significant weight, particularly those in the height range of 20 m to 30 m, the influence of pier inertia on the earthquake response of the pier responding as a vertical beam shall be considered. The pier weight distribution shall be represented by at least four weights along the pier height. Where analysis of vertical earthquake response is required by Clause 15.4, or for the analysis of horizontal earthquake response for bridges with spans longer than 40 m with significant transverse flexibility of superstructure, the superstructure weight of the span under consideration and of the adjacent spans, if any, shall be distributed to not less than four locations along the span. Where the superstructure is supported on bearings whose flexibility in the direction considered is such that superstructure displacements are expected to exceed pier headstock displacements by at least 200%, pier headstock weight and pier weight may be ignored. 15.3 Force-based design procedure
Design shall be undertaken for horizontal earthquake forces in both the longitudinal direction (i.e. span direction) and the transverse direction of the bridge. Design shall be undertaken for vertical earthquake forces where required by Clause 15.4. The longitudinal, transverse and (where required) vertical earthquake forces shall be assumed to act non-concurrently and shall be considered as separate load cases. A summary of the procedure is as follows: (a)
Determine the bridge earthquake design category and design performance level (Clauses 15.4 and 15.5).
(b)
Determine the probability factor and the hazard factor (Clause 15.6).
(c)
Determine the site subsoil class and hence the acceleration spectral shape factor (Clauses 15.7 and 15.8).
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(d)
Calculate the design action coefficient for earthquake response, based on the probability factor and hazard factor, the acceleration spectral shape factor, the fundamental natural period and the design ductility factor (Clause 15.9).
(e)
Calculate the earthquake forces and their distribution based on either static analysis (Clause 15.10) or dynamic analysis (Clause 15.11).
(f)
Determine the required design strength of bridge members (Clause 15.14), determine the abutment forces (Clause 15.15) and provide structural detailing for earthquake effects (Clause 15.16).
15.4 Bridge earthquake design categories (BEDC) and analysis requirements 15.4.1 BEDC classification
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Bridges and associated structures, such as approach retaining walls, shall be classified by the relevant authority or, if not classified by the relevant authority, they shall be classified as follows: (a)
BEDC-4 Bridges and associated structures that are essential to post-earthquake recovery, as specified by the relevant authority, and major bridges whose operation is essential to economic viability at state or national levels.
(b)
BEDC-3 Bridges that are designed to carry high volumes of road, rail or pedestrian traffic, or bridges over other high traffic volume roadways, railways or buildings.
(c)
BEDC-2 Minor bridges of two or more spans, and not covered by BEDC-3 or BEDC-4.
(d)
BEDC-1 Minor single span bridges carrying infrequent traffic, and not covered by BEDC-2, 3, or 4.
In situations where a bridge spans a road and/or rail of a higher category, the higher category shall be adopted for the bridge design. 15.4.2 Requirements for BEDC-1
Bridge structures in BEDC-1 need not be analysed for earthquake forces. The minimum lateral restraint provisions of Clause 10 of this Standard shall apply. The minimum bearing seat width measured normal to the face of an abutment or pier shall be 0.3 m. 15.4.3 Requirements for BEDC-2
For bridge structures in BEDC-2, the effects of earthquake actions shall be determined using either static analysis in accordance with Clause 15.10 or dynamic analysis in accordance with Clause 15.11. For all bridges in BEDC-2, vertical earthquake effects need not be considered. Abutment forces shall be determined using the procedure in Clause 15.15. The detailing of structural members, restraining devices, bearings and deck joints shall be in accordance with Clause 15.16. 15.4.4 Requirements for BEDC-3
Where there is a clear dominant mode of response in a particular direction, horizontal or vertical, the effects of earthquake actions shall be determined using either static analysis in accordance with Clause 15.10, or dynamic analysis in accordance with Clause 15.11. Where two or more modes each contribute at least 10% to response displacements or forces in a particular direction, the effects of earthquake actions shall be determined using a dynamic analysis in accordance with Clause 15.11.
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For all bridge structures in BEDC-3, the effects of both horizontal and vertical earthquake actions, and the P- effects shall be considered. Abutment forces shall be determined in accordance with Clause 15.15. The detailing of structural members, restraining devices, bearings and deck joints shall be in accordance with Clause 15.16. 15.4.5 Requirements for BEDC-4
Where there is a clear dominant mode of response in a particular direction, horizontal or vertical, the effects of earthquake actions shall be determined using either static analysis in accordance with Clause 15.10, or dynamic analysis in accordance with Clause 15.11. Where two or more modes each contribute at least 10% to response displacements or forces in a particular direction, the effects of earthquake actions shall be determined using a dynamic analysis in accordance with Clause 15.11. For all bridge structures in BEDC-4, the effects of both horizontal and vertical earthquake actions, and the P- effects shall be considered. Abutment forces shall be determined in accordance with Clause 15.15. The detailing of structural members, restraining devices, bearings and deck joints shall be in accordance with Clause 15.16. 15.5 Design performance level
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The strength and serviceability design of bridges shall be calculated based on either the damage control performance level or the service (immediate use) performance level. After the occurrence of the design earthquake, a bridge designed for the damage control performance level shall retain its structural integrity. Parts of the bridge susceptible to damage by their contribution to energy dissipation during the design earthquake shall be designed in such a manner that the structure can sustain the actions resulting from use by emergency traffic, and that inspection/repairs can be performed. After the occurrence of the design earthquake, bridges designed for the service (immediate use) performance level shall be capable of being used immediately by vehicles and plant for disaster recovery operations and evacuation of the populace. There shall be no need to reduce ordinary traffic over the bridge, or to carry out immediate repairs. Unless otherwise specified by the relevant authority, bridges shall be designed for the damage control performance level under the design earthquake. Where specified by the relevant authority, BEDC-4 bridges shall be designed for the service (immediate use) performance level under the design earthquake. 15.6 Probability factor (k p) and design seismic hazard factor (Z)
Unless otherwise specified by the relevant authority, bridges shall be designed for an annual probability of exceedance in accordance with Table 15.6. The probability factor (kp) shall be determined from the annual probability of exceedance in accordance with AS 1170.4. Unless determined by a site-specific seismology study approved by the relevant authority, the design seismic hazard factor (Z) shall be determined in accordance with AS 1170.4, but shall be not less than 0.08.
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TABLE 15.6 ANNUAL PROBABILITY OF EXCEEDANCE BEDC
Annual probability of exceedance (P)
4
1/2000
3
1/1000
2
1/500
1
Not applicable
15.7 Site subsoil class
The site subsoil class shall be determined in accordance with AS 1170.4—2007. For bridges with pile-supported foundations, the site subsoil class shall be based on the upper layers of the soil profile. 15.8 Acceleration spectral shape factor [Ch(T)]
The period-dependent acceleration spectral shape factor Ch(T) shall be as given in Table 6.4 of AS 1170.4. 15.9 Seismic acceleration for earthquake response Accessed by CENTRAL QUEENSLAND UNIVERSITY on 06 Jun 2017 (Document currency not guaranteed when printed)
15.9.1 Seismic acceleration for elastic horizontal earthquake response
The design action coefficient for elastic horizontal earthquake response [C(Tf)] shall be determined using the following equation:
C Tf kp ZCh Tf
. . .15.9.1
where Tf
= fundamental natural period of vibration of the bridge frame in the direction considered (longitudinal or transverse)
kp
probability factor, given in Clause 15.6
Z
design seismic hazard factor, given in Clause 15.6
Ch(Tf) = acceleration spectral shape factor at fundamental natural period of vibration of the bridge frame in the direction considered (longitudinal or transverse) (see Clause 15.8) 15.9.2 Seismic acceleration for ductile horizontal earthquake response
The value of design action coefficient Cd(Tf) for ductile response shall be calculated by dividing the design action coefficient for elastic horizontal earthquake response [C(Tf)] by the design ductility factor () in accordance with the following equation: Cd Tf
C Tf
kp ZCh Tf
. . . 15.9.2
where C(Tf)
= design action coefficient for elastic horizontal earthquake response, given in Clause 15.9.1
= design ductility factor
The design ductility factor ( ) is dependent on the particular configuration details of the bridge, the seismic detailing, and the axial load in concrete substructure components, as given in Table 15.9.2.
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AS 5100.2:2017
TABLE 15.9.2 DESIGN DUCTILITY FACTOR Design ductility factor ( )
Material
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Pier
Bridge configuration detail
Superstructure
Concrete
Any
Superstructure on elastomeric bearings without translational movement restraint in the direction considered
Concrete
Any
Superstructure on fixed pot or spherical bearings or elastomeric bearings with translational movement restraint in the direction considered at piers on:
Damage control performance level
Service (immediate use) performance level
1.5
1.0
-
stiff foundations (i.e. with negligible translational and rotational movements)
4.0
2.0
-
flexible foundations with significant contribution to the displacement at pier top (i.e. piles in 10 m or more of soft soil)
3.0
1.5
Concrete
Concrete
Piers integral with superstructure, and superstructure on bearings at abutments
4.0
2.0
Concrete
Concrete
Abutments integral with superstructure
2.0
1.25
Concrete
Any
Concrete pier/piles without stiff pile caps
2.0
1.25
Concrete
Any
Hollow reinforced concrete piers
2.0
1.25
Concrete
Any
Wall-type (blade wall) piers (see Note 9)
2.0
1.25
Steel
Any
Steel piers
2.0
1.25
Prestressed concrete
Any
Prestressed concrete piers with: -
bonded strands
2.0
1.25
-
external or un-bonded strands
1.0
1.0
NOTES: 1
Where more than one of the bridge configuration details in the table applies, the lowest design ductility factor shall be adopted.
2
Different values for the design ductility factor may apply in transverse and longitudinal directions.
3
For the purpose of seismic design wall-type piers have a width-to-thickness ratio of 4 or greater.
4
The design ductility factor for vertical response shall be taken as 1.0 for both damage control and service performance levels.
5
For concrete piers with N * 0.2ϕN uo a ductility factor of 3.0 for the damage control performance level and 1.5 for the service (immediate use) performance level may be adopted for horizontal response, where N * , ϕ and N uo are as defined in AS 5100.5.
6
For concrete piers with N * 0.2ϕN uo and with full seismic detailing in accordance with AS 5100.5, a ductility factor of 4.0 for the damage control performance level and 2.0 for the service (immediate use) performance level may be adopted for horizontal response, where N * , ϕ and N uo are as defined in AS 5100.5.
7
For concrete piers with N * > 0.2ϕN uo and with full seismic detailing in accordance with AS 5100.5, a ductility factor of 3.0 for the damage control performance level and 2.0 for the service (immediate use) performance level may be adopted for horizontal response, where N * , ϕ and N uo are as defined in AS 5100.5.
8
The application of Notes 5, 6 and 7 are subject to the approval of the relevant authority.
9
For concrete wall-type (blade wall) piers, the design ductility factor specified in this Table applies only in the transverse direction (that is, parallel to the long direction of the wall). In the longitudinal direction the appropriate pier design ductility factor applies.
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15.9.3 Seismic acceleration for elastic vertical earthquake response
The design action coefficient for elastic vertical earthquake response (upwards and downwards) shall be taken equal to two-thirds of the design action coefficient for elastic horizontal response given by Clause 15.9.1. 15.10 Earthquake forces determined from static analysis 15.10.1 Bridge frame horizontal earthquake force
The bridge frame horizontal earthquake force (FF) in the longitudinal or transverse direction shall be determined from the following equation: n
FF
= Cd Tf Wi
. . . 15.10.1
i 1
where
Wi
= one of the n individual weights representing the bridge frame, determined in accordance with Clause 15.2.2
Tf
= fundamental natural period of the bridge in the direction considered
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Cd(Tf) = value of the design action coefficient for ductile response, determined in accordance with Clause 15.9.2 15.10.2 Bridge frame vertical earthquake force
The bridge frame vertical earthquake force (FF) shall be determined from Equation 15.10.1 using the design action coefficient for elastic vertical earthquake response [Cd( Tf)] determined in accordance with Clause 15.9.3. 15.10.3 Distribution of the bridge frame earthquake force
The bridge frame earthquake force ( FF) shall be distributed to the n bridge frame weight locations (Wi) using the following equation:
Fi
=
FF
Wii n
W i 1
. . . 15.10.3
i i
where Fi
= bridge frame earthquake force at bridge frame weight location Wi
i
= value of normalized fundamental displacement mode shape at the location of weight Wi
Wi
= one of the n individual weights representing the bridge frame, determined in accordance with Clause 15.2.2
15.11 Earthquake forces determined from dynamic analysis
Where required or used, dynamic analysis shall be carried out in accordance with AS 1170.4, except as noted in this Clause. The dynamic analysis procedure shall be either a modal-response-spectrum analysis or a time-history analysis. Both elastic and inelastic time-history analysis approaches may be used as alternatives to modal-response-spectrum analysis. When inelastic time-history analysis is adopted, hysteretic rules shall be appropriate for the materials and sections modelled. Response values from time-history analysis shall be based on the average of results from not less than five appropriate spectrum-compatible accelerograms representing the site seismicity. Standards Australia
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AS 5100.2:2017
Regardless of which dynamic analysis method is adopted, member stiffness and weight distribution shall comply with Clause 15.2.1 and Clause 15.2.2 respectively. 15.12 Seismic displacements
The displacements of the bridge frame shall be calculated using the design action coefficient for elastic horizontal or vertical earthquake response (as appropriate) determined in accordance with Clause 15.9.1 or 15.9.3 respectively. 15.13 P-Δ moments
Moments resulting from the weight supported by a pier acting through seismic displacements (P-Δ moments) shall be calculated for bridges in BEDC-3 and BEDC-4. The seismic displacements shall be calculated in accordance with Clause 15.12. P-Δ moments shall not exceed 30% of the pier-base moment demand for the relevant earthquake load case combination.
For concrete piers, the earthquake design moment shall be increased by 50% of the calculated P-Δ moment where the P-Δ moment exceeds 10% of the pier-base moment demand for the relevant earthquake load case combination.
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For steel piers, the earthquake design moment shall be increased by 100% of the calculated P-Δ moment when the P-Δ moment exceeds 5% of the pier-base moment demand for the relevant earthquake load case combination. 15.14 Required strength of bridge members
The ultimate strength of bridge members, calculated in accordance with AS 5100.5, AS/NZS 5100.6 or AS 5100.9, as appropriate, shall be not less than the actions resulting from the ULS load combinations in Clause 23.3. 15.15 Design abutment forces
Unless subject to special study, the abutment forces determined from the static or dynamic analysis shall be multiplied by the design ductility factor () to obtain the design abutment forces. 15.16 Structural detailing requirements for earthquake moments 15.16.1 General
Detailing requirements for structural members under earthquake moments shall be as specified in AS 5100.5. Particular attention shall be given to the prevention of dislodgement of the superstructure from its support system (see Clause 15.16.2). Particular attention shall be given to the provision of viable, continuous and direct load paths from the level of the bridge deck to the foundation system. 15.16.2 Deck joints and bearings
Deck joints are not required to accommodate the horizontal movements due to the design seismic action. The detailing of deck joints expected to be damaged due to the design seismic action shall allow for a predictable mode of damage and an anticipated method of repair. The consequent distribution and magnitude of earthquake forces in the bridge shall be fully evaluated and considered in the design of all structural elements. Fixed bearings shall be designed for earthquake actions. Where these actions are outside the range of conventional bearings, measures shall be provided to prevent dislodgment of the superstructure from the support structure. Such other measures shall be designed to withstand the design earthquake forces, or the minimum lateral restraint force specified in Clause 10, whichever is the greater. The influence of such measures on the distribution and magnitude of earthquake forces in the bridge shall be fully evaluated and considered in the www.standards.org.au
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design of all structural elements. Vertical restraint devices shall be provided at all supports where the vertical design earthquake force opposes and is greater than 50% of the static reaction under permanent effects. The vertical restraint device shall be designed to resist an uplift force of not less than 10% of the vertical reaction at the support due to permanent effects. Vertical design earthquake forces (when applicable) shall be considered in the design of horizontal restraints that rely on any component of friction. Movement bearings are not required to accommodate the horizontal movements due to the design seismic action. The detailing of bearings expected to be damaged due to the design seismic action shall allow for a predictable mode of damage and an anticipated method of repair. The consequent distribution and magnitude of earthquake forces in the bridge shall be fully evaluated and considered in the design of all structural elements. At expansion ends of the superstructure (including movement joints at an abutment, pier or internal hinge) the superstructure shall overlap the substructure by a sufficient distance to prevent loss of support to the superstructure due to the design seismic action. Sufficient overlap length (as shown in Figure 15.16.2) shall be provided to accommodate the relative longitudinal seismic displacement. The minimum overlap length measured normal to the face of an abutment or pier (Lbs) shall satisfy the following: Lbs
= 1.25∆L + 0.0004Ld + 0.007 hd + 0.005 B 0.3
∆L
= longitudinal seismic displacement at the abutment, in metres
Ld
= length of the superstructure to the next expansion joint, in metres
hd
= average height of piers supporting the superstructure length Ld, in metres
. . . 15.16.2
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where
B
length of the bearing seat transverse to the bridge longitudinal axis, in metres
L bs
L bs L bs A but m e nt
L bs Pi er
Inter nal hin g e
FIGURE 15.16.2 OVERLAP LENGTH L bs
15.16.3 Pile to pile cap ductile connections
For bridge structures of BEDC levels 2, 3 or 4, the connection between each pile and its pile cap shall be designed to resist tensile force levels predicted by the analysis, but not less than 10% of the pile ultimate axial compression force (N*).
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16 FORCES RESULTING FROM WATER FLOW 16.1 General
Bridges that cross a river, stream or any other body of water shall be designed to resist the effects of water flow and wave action, as applicable. The design shall include an assessment of how the water forces may vary in an adverse manner under the influence of debris, log impact, scour and buoyancy of the structure. Tidal and wave actions shall be considered on bridges across large bodies of water, estuaries and open sea. NOTE: Wave action on bridges is not covered in this Standard. Refer to specialist literature.
16.2 Water flow velocity
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Water flow forces for each limit state are dependent on a water flow velocity (V) applicable to the structural element under consideration. For the equations in this Clause (16), the particular choice of V shall depend on hydraulic considerations as follows: (a)
For substructures, V shall be the velocity of flow for the critical average recurrence interval (ARI) through the bridge opening averaged over the depth of flow and over the relevant bridge span.
(b)
For superstructures and debris loading, V shall be the approach surface velocity for the critical ARI just upstream of the bridge. NOTE: For wide flood plains, the watercourse may require guide banks.
(c)
For log and vessel impact, the relevant approach velocity shall be at the level of impact being considered; and for surface impact, this shall be taken as 1.4 times the average velocity.
(d)
The adverse structural effect of local scour shall be taken into consideration in the design at each limit state. Where widespread, various amounts of bed scour shall be considered. NOTE: The beneficial effect of bed scour in reducing velocity should generally be neglected except where widespread mobile alluvium is evident and velocities can be relied upon to occur for the flood event under consideration.
16.3 Limit states 16.3.1 ULSs
The ULSs defined in AS 5100.1 Clause 6.3 shall be satisfied for all floods up to and including the 2000 year ARI flood. A load factor of 1.3 shall be used. 16.3.2 SLSs
The SLSs defined in AS 5100.1 Clause 6.3 shall be satisfied for all floods up to and including the SLS flood defined in AS 5100.1 Table 11.1. A load factor of 1.0 shall be used. 16.4 Forces on piers due to water flow 16.4.1 Drag forces on piers
In bridge structures subjected to water flow effects, the fluid forces on the piers are dependent on the pier shape, pier configuration, the water velocity and the direction of the water flow. The design drag forces (Fd) parallel to the plane containing the pier shall be calculated as follows: Fd = 0.5 CdV2Ad
. . .16.4.1
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Cd = drag coefficient, depending on pier shape (see below) Ad
= wetted area of the pier normal to the water flow, equal to the thickness of the pier normal to the direction of the water flow multiplied by the height of the water flow. Consideration shall be given to variations of the direction of the water flow.
In the absence of more exact estimates, the value of Cd shall be assumed as follows: Cd = 0.7
(semi-circular pier nosing)
= 1.4
(square end pier nosing)
= 0.8
(90° or sharper wedge, nosing with an angle of 90° or less)
NOTE: For a diagrammatic view of typical pier end configurations, see Figure 16.4.1.
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Water fl ow d ire c t i o n
(a) S e m i - c ir c u l ar p i er n o s i n g
Water fl ow d ire c t i o n
(b) S q u ar e e n d p i er n o s i n g
Water fl ow d ire c t i o n
(c) 9 0 ° or s har p er we d g e n o s in g (w it h an g l e 9 0 ° or l e s s)
FIGURE 16.4.1 TYPICAL PIER END CONFIGURATIONS
16.4.2 Side forces on piers
The design side forces ( FL), perpendicular to the plane containing the pier, as shown in Figure 16.4.2, shall be calculated as follows: FL = 0.5 CsV2AL Standards Australia
. . .16.4.2
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where Cs
= side force coefficient (which depends on the angle between the water flow direction and the plane containing the pier)
AL = wetted area of the pier, equal to the width of the pier parallel to the direction of the water flow multiplied by the height of the water flow
In the absence of more exact estimates, the value of Cs shall be assumed as follows: Cs
= 0.9 for θw 30° = 1.0 for θw > 30°
where θw is the angle between the direction of the water flow and the transverse centre-line of the pier.
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Fd
Fd
FL FL D ire c t i o n of water fl ow
D ire c t i o n of water fl ow
θw
θw
Centre - line of p i er PL AN
Centre - line of p i er
ISO M E TRIC VIE W
LEGEND: F d = design drag force F L = design side force
FIGURE 16.4.2 DRAG AND SIDE FORCES ON PIERS
16.5 Forces on superstructures due to water flow 16.5.1 General
A superstructure that is partially or fully submerged in a flood is subjected to— (a)
a drag force normal to its longitudinal axis;
(b)
a vertical lift force (positive upwards); and
(c)
a moment about the girder soffit level (clockwise positive with the water flow from left to right).
The loads specified in Items (a), (b) and (c) shall be determined in accordance with Clauses 16.5.2, 16.5.3 and 16.5.4, as appropriate.
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16.5.2 Drag force on superstructures
The design drag force (Fd) on superstructures shall be calculated as follows: Fd = 0.5 CdV2As
. . .16.5.2(1)
where Cd = drag coefficient
= net wetted area of the superstructure, including any railings or barriers, projected on a plane normal to the water flow
As
The value of Cd for superstructures shall be obtained from Figure 16.5.2(A). The relative submergence (Sr) and the proximity ratio (Pr) shall be calculated as follows: Sr
Pr
d wgs
. . . 16.5.2(2)
d sp
y gs
. . .16.5.2(3)
d ss
dwgs = vertical distance from the girder soffit to the flood water surface upstream of the bridge [see Figure 16.5.2(B)] dsp = wetted depth of the superstructure (including any railings or barriers) projected on a plane normal to the water flow [see Figure 16.5.2(B)] ygs = average vertical distance from the girder soffit to the bed assuming no scour at the span under consideration [see Figure 16.5.2(B)] dss = wetted depth of the solid superstructure (excluding any railings but including solid barriers) projected on a plane normal to the water flow [see Figure 16.5.2(B)]
4.0
DR AG COEFFICIENT ( C d )
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where
3.8 3 .6 3 .4 3.2 3 .0 2.8 2.6 2.4 2. 2 2.0 1.8 1.6 1.4 1. 2 1.0
P r = 1. 5
P r = 2. 5 Pr = 3.5 Pr ≥ 8 Lin ear inter p o l at i o n of inter m e d i ate valu e s i s p er m iitt te d 0. 5
1.0
1. 5
2 .0
2. 5
3 .0
3.5
4.0
REL ATIVE SU B M ERGEN CE, ( S R )
FIGURE 16.5.2(A) SUPERSTRUCTURE C d
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Ca se 1: Fully su b m er g e d
Fl o o d l eve l
d wgs
d wgs
dss = dsp
dsp dss
D ire c t i o n of water fl ow
ygs
ygs
D ire c t i o n of water fl ow
B e d l eve l
Ca se 2: Par t i ally su b m er g e d Fl o o d l eve l
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dss = dsp = d wgs
dss = dsp = d wgs
D ire c t i o n of water fl ow
ygs
ygs
D ire c t i o n of water fl ow
B e d l eve l
FIGURE 16.5.2(B) SUPERSTRUCTURE DRAG FORCE DIMENSIONS
16.5.3 Lift force on superstructures
The design lift force (FL) on a superstructure shall be calculated as follows:
FL = 0.5 CLV2AL
. . . 16.5.3
where
CL = lift coefficient AL = plan deck area of the superstructure The value of CL shall be obtained from Figure 16.5.3. An upward and downward lift force shall be calculated at each Sr. The upward and downward lift force shall be combined with the moment as described in Clause 16.5.4 to determine the maximum uplift forces and downward forces acting on various elements of the bridge.
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LIF T COEFFICIENT ( C L )
AS 5100.2:2017 1.0 0.8 0.6 0.4 0. 2 0.0 - 0. 2 - 0.4 - 0.6 - 0.8 -1.0 -1. 2 -1.4 -1.6 -1.8 -2.0 -2. 2 0. 5
1.0
1. 5
2.0
2. 5
3 .0
3.5
4.0
REL ATIVE SU B M ERGEN CE ( S r )
FIGURE 16.5.3 SUPERSTRUCTURE C L
The drag and lift forces generate a moment about the longitudinal axis of the superstructure. The design superstructure moment due to water flow (Mg) at the soffit level at the centreline of the superstructure shall be calculated as follows:
Mg = 0.5 CmV2Asdsp
. . . 16.5.4
where
Cm = moment coefficient The value of Cm shall be obtained from Figure 16.5.4.
6.0
M O M ENT COEFFICIENT ( C m )
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16.5.4 Moment on a superstructure
5. 5
P r = 1. 5 Pr = 3.5
5.0 4. 5 4.0 3.5
P r ≥ 6. 5
3 .0 2.5 2.0 1. 5
Lin ear inter p o l at i o n of inter m e d i ate valu e s i s p er m i t te d
1.0 0. 5 0.0 0. 5
1.0
1. 5
2.0
2. 5
3 .0
3.5
4.0
REL ATIVE SU B M ERGEN CE ( S r )
FIGURE 16.5.4 SUPERSTRUCTURE C m
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16.5.5 Loads on superstructures with superelevation
The loads on a superstructure with a positive superelevation (upstream face raised) of up to 4% shall be calculated in accordance with Clauses 16.5.2 to 16.5.4. The loads on a superstructure with a negative superelevation of up to 4% shall be calculated in accordance with Clauses 16.5.2 to 16.5.4, but with the following adjustments to the coefficients: (a)
The value of Cd shall be increased by 5%.
(b)
The magnitude of CL shall be increased by 20%.
(c)
The value of Cm shall be the same as for a level superstructure.
If the superelevation is greater than 4%, the upward lift force shall be calculated as for wall type piers in accordance with Clause 16.4.2, except that AL shall be taken as the plan deck area and shall be taken as 0.9. For superelevation outside this range, study of specialist literature or physical model testing shall be undertaken. 16.6 Forces due to debris
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16.6.1 Depth of debris mat
The depth of a debris mat varies depending on factors such as catchment vegetation, available water flow depth and superstructure span. In the absence of more accurate estimates, the minimum depth of debris mat for design shall be 1.2 m and the maximum depth shall be 3 m, or as specified by the relevant authority. 16.6.2 Debris acting on piers
A debris load acting on piers shall be considered for bridges where the flood level is below the superstructure. The length of a debris mat shall be taken as one-half the sum of the adjacent spans or 20 m, whichever is the lesser. The debris load shall be applied at midheight of the debris mat, assuming the top of the debris mat is at the flood level. 16.6.3 Debris acting on superstructures
A debris load acting on superstructures shall be considered for bridges where the flood level is above a level of 600 mm below the soffit level. The length of the debris mat shall be the projected length of the superstructure. The debris load shall be applied at mid-height of the submerged superstructure, including any railing or barriers, where appropriate. 16.6.4 Calculation of debris load
The ultimate and serviceability design drag forces (Fd) due to debris shall be calculated using the following equation:
Fd = 0.5 CdV2Adeb
. . . 16.6.4
where
Cd = obtained from Figure 16.6.4(A), for debris acting on piers = obtained from Figure 16.6.4(B), for debris acting on superstructures
Adeb = projected area of debris NOTE: The depth of debris varies depending on the catchment vegetation.
Lateral water flow forces shall not act concurrently on parts of the bridge subject to debris loading. Lift forces and moments due to water flow or debris loading shall be considered where the superstructure is completely or partially submerged.
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DR AG COEFFICIENT ( C d )
AS 5100.2:2017 3 .6 3 .4 3.2 3 .0 2.8 2.6 2.4 2. 2 2.0 1.8 1.6 1.4 1. 2 1.0
V = ve lo cit y of water flow (m /s) y = average flow depth (m)
0
40 20
80 60
120 16 0 20 0 24 0 28 0 3 20 3 6 0 4 0 0 10 0 14 0 18 0 2 20 26 0 3 0 0 3 4 0 3 8 0 V 2y
FIGURE 16.6.4(A) PIER DEBRIS Cd
F = V/√(gy) where: V = ve l o c it y of water fl ow (m /s) y = aver ag e fl ow d e pt h (m) g = ac c e l er at i o n d u e to gr av it y (m /s 2)
5.6 5. 2 DR AG COEFFICIENT ( C D )
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6.0
4.8 4.4 4.0 3 .6 3.2
F = 0. 2
Linear interpolation of intermediate valu e i s p er m iitt te d
2.8 F = 0.3
2.4
F = 0.4
2.0
F = 0. 5
1.6 1. 2
F = 0.6
0.8 0.4
0. 5 1.0 1. 5 2 .0 2. 5 3 .0 3 . 5 4.0 4. 5 5.0 5. 5 6.0 6. 5 7.0 7. 5 8 .0 8. 5 9.0 9. 5 10.010. 5 PROXIMIT Y R ATIO ( P r )
FIGURE 16.6.4(B) SUPERSTRUCTURE DEBRIS C d
16.7 Forces due to moving objects 16.7.1 General
The forces due to moving objects and debris shall not be applied concurrently. Moving object impact forces shall be applied with such other water flow forces as appropriate.
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AS 5100.2:2017
16.7.2 Log impact
Where floating logs are possible, the ultimate and serviceability design forces exerted by such logs directly hitting piers or superstructure shall be calculated on the assumptions that a log with a minimum mass of 2 t will be stopped within a distance of 300 mm for timber piers, 150 mm for hollow concrete piers, and 75 mm for solid concrete piers. If fender piles or sheathing, to absorb the energy of the blow, are placed upstream from the pier, the stopping distance shall be increased. The design forces shall be calculated using the water flow velocity at the surface of water flow at the flood level relevant for the SLS, or for ULS, as appropriate. 16.7.3 Large item impact
In urban areas, the effects of impact and buoyancy from large floating items such as pontoons, pleasure craft, shipping containers, and the like, shall be considered. The type and size of large items considered shall be subject to approval of the relevant authority. The forces due to log impact or large item impact shall not be applied concurrently. 16.8 Effects due to buoyancy and lift
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In assessing the effects of buoyancy and lift on bridge structures, consideration shall be given to the following: (a)
The effects of buoyancy and lift on substructure, including piling, and superstructure dead loads. Buoyancy shall be applied concurrently with other water flow forces.
(b)
The provision of effective bleed holes, which dissipate air trapped between high water level and the underside of the deck slab, and reduce the effect of buoyancy for beam and slab or box girder bridges.
(c)
Provision of drainage from internal cells.
A positive tie-down system shall be provided for the superstructure if uplift occurs at any support or bearing, taking account of dead loads, buoyancy, water flow forces and debris loading. The tie-down shall be designed for an ultimate force equal to: * WF FLu* M Lu / Z Buoyancy g G
. . . 16.8
where
WF = ultimate load factor for forces resulting from water flow, see Clause 16.3.1 g
= ultimate load factor for dead load that reduces safety, given in Table 6.2
G
= dead load reaction on the support
Z
= bearing layout modulus
* FLu = ultimate design lift force * M Lu = ultimate moment due to water flow and/or debris loading, as applicable
The bearings shall be adequately restrained in position during submergence of the superstructure.
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17 WIND LOADS 17.1 General
This Clause (17) specifies design wind loads for conventional bridge structures. For windsensitive structures, such as suspension or long-span cable-stayed bridges, which may be subject to wind-excited oscillations, special investigations into the dynamic behaviour of the structure shall be carried out. Wind loads on lighting, traffic signal and traffic sign structures shall be in accordance with Clause 24. Wind loads on noise barriers shall be in accordance with Clause 25. The effect of wind on road traffic need not be considered 17.2 Design wind speed 17.2.1 General
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The design wind speed shall be derived from the appropriate regional basic design wind speeds, after adjustment for— (a)
average return interval;
(b)
geographical location;
(c)
terrain category;
(d)
shielding; and
(e)
height above ground.
The average return interval (ARI) shall be as specified in Clause 17.2.2. The values and factors for Items (b) to (e) shall be obtained from AS/NZS 1170.2. 17.2.2 Average return interval
The design wind speed for the average return interval (ARI) shall be as specified in AS/NZS 1170.2 for that return interval. The average return interval (ARI) to be adopted shall be as follows: (a)
For ULSs ................................................................................................... 2000 years.
(b)
For SLSs ......................................................................................................... 20 years (for wind in conjunction with permanent effects only).
17.3 Transverse wind load 17.3.1 Calculation of transverse wind load
The transverse wind load shall be taken as acting horizontally at the centroids of the appropriate areas, and shall be calculated using the following equations: (a)
Ultimate design transverse wind load ( Wt* ): Wt* 0.0006 Vu2 At Cd
(b)
. . . 17.3(1)
Serviceability design transverse wind load (Wt): Wt 0.0006 Vs2 At Cd
. . . 17.3(2)
where
Vu
= design wind speed for ULSs
Vs
= design wind speed for SLSs
At
= area of the structure for calculation of wind load
Cd = drag coefficient Standards Australia
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AS 5100.2:2017
17.3.2 Area of structure for calculation of transverse wind load (At)
The area of the structure or element under consideration shall be the solid area in normal projected elevation, subject to the following: (a)
Superstructures with solid barriers The area of the superstructure shall include the area of the solid windward barrier. (The effect of the leeward barrier need not be considered.)
(b)
Superstructures with open barriers The total load shall be the sum of the loads for the superstructure, the windward barrier and the leeward barrier considered separately. Where there are more than two barriers or safety fences, irrespective of the width of the superstructure, only those two elements having the greatest unshielded effect shall be considered.
(c)
Piers Shielding shall not be considered.
17.3.3 Drag coefficient (Cd )
The drag coefficient (Cd ) shall be determined as follows: (a)
Drag coefficient for all superstructures with solid elevation For superstructures with or without traffic load, Cd shall be as shown in Figure 17.3.3,
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where
b = overall width of the bridge between outer faces of barriers d = depth of superstructure, including solid barrier, if applicable (b)
Aerodynamic shape factor for truss girder superstructures The wind force on truss girder superstructures shall be calculated by considering each component individually, using the aerodynamic shape factor specified in AS/NZS 1170.2.
(c)
Drag coefficients for beams during erection The drag coefficient for beams and girders during erection shall be calculated for individual beams as shown in Figure 17.3.3. Shielding shall not be considered for individual beams. Shielding may be allowed for when two or more beams are connected, provided the ratio of the clear distance between beams to the beam depth is not greater than 7. Where the ratio of the clear distance between connected beams to the beam depth is greater than 7, the drag coefficient for the combination shall be taken as 1.5 times the value for an individual beam.
(d)
Aerodynamic shape factor for barrier railings, barriers and substructures Aerodynamic shape factors shall be obtained from AS/NZS 1170.2.
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DR AG COEFFICIENT C d
2.8
Minimum c o ef fi c i ent for d e c ks su p p or te d by I se c t i o n s, m ore t han 4 b eam s or b ox- g ir d er s
2.4 2.0 1.6 1. 2 0.8 0.4 0 0.4 0.8 1.2 1.6 2.0
2
6 10
14 18 22 26 30
R ATIO b/d
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NOTES: 1
The values given assume a vertical elevation and a horizontal wind.
2
Where the windward face is inclined to the vertical, the drag coefficient (C d ) may be reduced by 0.5% per degree of inclination from the vertical, subject to a maximum reduction of 30%.
3
Where the windward face consists of a vertical and a sloping part or two sloping parts inclined at different angles, the wind load shall be derived as follows: (a)
The drag coefficient (C d ) shall be calculated using the total depth of the structure.
(b)
For each non-vertical face, the basic drag coefficient (C d ) calculated above shall be reduced by 0.5% per degree of inclination from the vertical, subject to a maximum reduction of 30%.
(c)
The total wind load shall be calculated by applying the appropriate drag coefficients to the relevant areas.
4
Where a superstructure is superelevated, C d shall be increased by 3% per degree of inclination to the horizontal, but not by more than 25%.
5
Where a superstructure is subject to wind inclined at not more than 5 to the horizontal, C d shall be increased by 15%. Where the angle of inclination exceeds 5, the drag coefficient shall be derived from tests.
6
Where a superstructure is superelevated and subject to inclined wind, Cd shall be the subject of special investigation.
FIGURE 17.3.3 DRAG COEFFICIENT (C d) FOR SUPERSTRUCTURES WITH SOLID ELEVATION
17.4 Longitudinal wind load
For piers, truss bridges and other superstructure forms that present a significant surface area to wind loads parallel to the longitudinal centre-line of the structure, a longitudinal wind load shall be considered. The ultimate and serviceability design longitudinal wind loads shall be calculated in a manner similar to those for transverse wind loads. NOTE: Longitudinal wind loads on the superstructure may also be significant during the construction stage of some bridge types that are not affected by these loads during service.
17.5 Vertical wind load
An upward or downward vertical wind load, acting at the centroid of the appropriate area, shall be calculated using the following equations: (a)
Ultimate design vertical wind load ( Wv* ):
Wv* 0.0006 Vu2 Ap CL (b)
. . . 17.5(1)
Serviceability design vertical wind load ( Wv ):
Wv 0.0006 Vs2 Ap CL
. . . 17.5(2)
where Standards Australia
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Vu
= design wind speed for ULSs
Vs
= design wind speed for SLSs
Ap
= bridge area in plan
AS 5100.2:2017
CL = lift coefficient = 0.75 Equations 17.5(1) and 17.5(2) may be used for an angle of inclination of the wind to the structure is less than 5°. For inclinations greater than 5, the lift coefficient shall be investigated by testing. 17.6 Wind load on rail traffic
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The effect of wind load on rail traffic shall be included in both ULS and SLS load combinations and shall be considered to act with the design rail traffic load. The area to be considered in the calculation of the wind load on rail traffic shall be the solid area in normal projected elevation of the train area where it protrudes beyond the projected elevation of the bridge structure. For the calculation of the projected area, a train shall be assumed to be carrying double stacked containers 7.0 m in height taken from the top of rails. The point of application shall be taken as 3.5 m above the top of the rails. For lines where there is no provision for double stacked container traffic to operate, the height of the highest wagon or carriage shall be used with the application of the wind force at mid height. In no case shall the train height be less than 4.0 m. The drag factor to be used in calculating the force for wind on the bridge shall be obtained from Clause 17.3.3(a), with the depth of superstructure d taken as the projected overall depth of the train and bridge superstructure, and the width b as specified in Clause 17.3.3(a). 17.7 Combination of wind loads
The vertical wind load shall be considered to act concurrently with the other wind loads so as to produce the most adverse effect. The critical combination shall be treated as a single transient effect. 18 THERMAL EFFECTS 18.1 General
Daily and seasonal fluctuations in air temperature and solar radiation cause both variations in average bridge temperature and differential temperature gradients across structural members. Variation in average bridge temperature shall be used as a basis for— (a)
assessment of bearing and deck joint movement requirements; and
(b)
evaluation of design loads or load effects resulting from the restraint of associated expansion or contraction by either the form of the structure, e.g. as in portal frames and arches, or by the support and bearing stiffnesses.
Differential temperatures within bridge superstructures result in load effects within the section. In the case of statically indeterminate or restrained structural forms, these differential temperatures also cause both longitudinal and transverse parasitic load effects, which shall be taken into account in the design.
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18.2 Variation in average bridge temperature
Extremes of shade air temperature appropriate to the structure location shall be derived from Table 18.2(A). Consideration shall be given to particular site characteristics (e.g. frost pockets and sheltered low-lying areas) where the minimum shade air temperature may be substantially lower; and in urban and coastal areas where the minimum values may be higher than the values given in Table 18.2(A). For major or special structures, extreme shade air temperatures for the actual site shall be determined. For minor structures, consideration shall be given to increase displacements determined for the range of average bridge temperatures to allow for limited supervision and control of setting bearings and deck joints.
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For concrete superstructures (Types 1 and 2 shown in Figure 18.3), the minimum and maximum average bridge temperatures shall be derived from the minimum and maximum shade air temperatures by reference to Table 18.2(B). Average temperature values indicated relate to bridge cross-sections with a depth of up to 2 m. Where sections are greater than 2 m in depth, reference shall be made to specialist literature to determine the heat sink effect. For superstructures consisting of a concrete deck on steel girders (Type 3 shown in Figure 18.3), the range of average bridge temperatures given in Table 18.2(B) shall be extended by reducing the minimum average temperature by 5°C and increasing the maximum average by 10°C. For superstructures consisting of a steel deck on steel girders, such as pedestrian bridges, the range of average bridge temperatures given in Table 18.2(B) shall be extended by reducing the minimum average temperature by 10°C and increasing the maximum average by 20°C. TABLE 18.2(A) EXTREMES OF SHADE AIR TEMPERATURES
Location
Height above sea level m
Shade air temperature °C Region I North of 22.5°S Max.
Inland
Coastal
Min.
Region II South of 22.5°S
Region III Tasmania
Max.
Min.
Max.
Min.
1000
46
0
45
5
37
5
>1000
36
5
36
10
32
10
1000
44
4
44
1
35
1
>1000
34
1
34
6
30
6
NOTE: Coastal locations are locations that are less than 20 km from the coast.
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AS 5100.2:2017
TABLE 18.2(B) AVERAGE BRIDGE TEMPERATURES Min. Shade air temp °C
Average bridge temp °C
8
2
2
4
4
8
10
12
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Max.
NOTE: Linear permitted.
50
54
46
50
42
46
38
43
34
40
30
37
interpolation
of
intermediate
values
is
18.3 Differential temperature
The effects of vertical differential temperature gradients through a bridge superstructure shall be derived for both positive temperature differential conditions, where solar radiation has caused a gain in top surface temperatures, and negative temperature differentials, where re-radiation of heat from the section results in relatively low top surface temperatures. Design-effective vertical temperature gradients, appropriate to various regions and superstructure types, shall be as shown in Figure 18.3. NOTE: These design temperature gradients have been derived for cases where decks are unsurfaced or where surfacing will be limited to 50 mm of bituminous concrete. For substantially greater thicknesses of surfacing, some reduction in design temperature gradients may be warranted.
For those parts of rail bridge decks covered by ballast greater than 100 mm thick, the differential temperature distribution shall be as given in Figure 18.3, provided the maximum temperature of the temperature profiles given apply at the top of the ballast, with a corresponding reduced temperature applying at the top of the bridge deck. The effects of transverse differential temperature gradients across the superstructure shall also be considered for some structures, such as very wide bridges. The effects of vertical and transverse differential temperatures shall be considered separately.
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Bridge type 1
Typical cross-section
Concrete beam and slab, and slab deck
Effective temperature gradient De c k c o n c rete sur fac e
De c k c o n c rete sur fac e
T
0.4T
T (°C)
300
5
y
T( y) = T
D
S of fi t
D
y D
S of fi t
20 0
S of fi t
5 - s of fit w it hin 8 m of g r o u n d 0 - over water
y (m m)
2
Concrete box girders and Super Tgirders
( 1 - 120y 0 )
(T+ 3) M a x. d = 3 0 0
T
0.4T
T(°C) d
300 y
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D
T(y) = T + 3 - 0.0 5y Te m p er ature profil e ac ro s s d e c k s l a b s over c l o se d b ox c e ll s (s had e d area)
D
M a x. d = 3 0 0
20 0 y D
5 or 0 (a s for Ty p e 1) y(m m)
5
T( y) = T
( 1 - 120y 0 )
DIMENSIONS IN MILLIMETRES
FIGURE 18.3 (in part) DESIGN EFFECTIVE VERTICAL TEMPERATURE GRADIENTS
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Bridge type 3
AS 5100.2:2017
Typical cross-section
Concrete slab on steel trough, steel box or steel I girders
Effective temperature gradient (T+ 8)
(T+5) t
M a x. d = 3 0 0 t
T(°C) d
y t
(0.4T - 3)
D
D
300 max.
T(y) = T + 3 - 0.0 5y (s had e d area)
(
T( y) = (T+ 5) 1 -
y 120 0
5
)
y D
y(m m)
Te m p er ature d e p e n d e nt o n d e c k t hi c k n e s s (t)
LEGEND: positive differential temperature gradients
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negative differential temperature gradients D
=
total depth of superstructure
d
=
thickness of the slab over a box cell (shown hatched)
T
=
temperature
t
=
thickness of the deck
y
=
variable distance taken in determining temperature change at T ( y )
NOTES: 1
Regional values for T:
2
Region T
Regional category
1
20°C
Continental-inland of Great Dividing Range or further than 200 km from coast (typical Canberra, Alice Springs)
2
18°C
Coastal temperature—No further than 200 km from coast (typical Perth, Adelaide. Melbourne, Sydney)
3
14°C
Coastal sub-tropical, monsoonal (typical Brisbane, Darwin)
The temperature gradient given for deck slabs forming closed box cells should only apply for slab thicknesses, including any internal fillets, of D less than 300 mm. Therefore, any deck slab, or part thereof, over a box cell with a thickness greater than 300 mm, should be subject to the general effective vertical temperature gradient shown. DIMENSIONS IN MILLIMETRES
FIGURE 18.3 (in part) DESIGN EFFECTIVE VERTICAL TEMPERATURE GRADIENTS
18.4 Limit states
Thermal effects shall be considered where they adversely affect a structure, as follows: (a)
For ULSs The thermal effects that are applicable to the structure, as determined from the relevant material Part of this Standard shall be considered. The ultimate design effects shall be determined using a load factor of 1.25.
(b)
For SLSs All thermal effects shall be considered. The serviceability design effects shall be determined using a load factor of 1.0.
The effects of vertical and transverse differential temperatures shall be considered separately.
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19 SHRINKAGE, CREEP AND PRESTRESS EFFECTS 19.1 Shrinkage and creep effects
Consideration shall be given to the effects of shrinkage and creep in concrete structures. The characteristics of different types and different ages of concrete shall be considered. Shrinkage and creep strains shall be calculated in accordance with AS 5100.5. The design effects shall be calculated using the nominal dead loads of the structure. A load factor of 1.2 for ULSs, and 1.0 for SLSs shall be used. Shrinkage and creep effects shall be included in serviceability design checks for stresses, cracking and deflection. Where shrinkage and creep affect the strength, stability or displacement limits of a structure or its components, these effects shall be taken into consideration. NOTE: For shrinkage and creep effects in timber structures, refer to AS 5100.9.
19.2 Prestress effects (PS)
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The secondary effects of prestress induced in restrained components and indeterminate structures shall be considered in the design of prestressed concrete structures. Where applicable, the prestressing effect shall be included with a load factor of 1.0 in all load combinations for both ultimate and serviceability design, except for the ULS case of dead load (G) plus prestress effect (PS) at transfer, where the more severe of the following combinations shall be used: 1.15G + 1.15PS and
. . . 19.2(1)
0.9G + 1.15PS
. . . 19.2(2)
20 DIFFERENTIAL MOVEMENT OF SUPPORTS 20.1 Differential settlement effects
Where differential settlement of the supports, specially in continuous span configurations, affects the structure in whole or in part, the effects shall be taken into consideration. Differential settlement shall be calculated assuming permanent loads only acting, and using the nominal dead loads of the structure, except that for rail bridges, the additional settlement due to traffic load, including the dynamic load allowance, shall be included. The differential settlement or rotation shall take account of the relief afforded by creep and soil-structure interaction. Design differential settlement effects shall be included in the SLSs for the structure, including bearings and deck joints using a load factor of 1.0. For rail bridges, spans shall be proportioned such that there is no net uplift at bearings. Consideration shall be given to whether differential settlement effects need to be included in the ULSs loads for the structure, using a load factor of 1.5. Where possible, all structures shall be designed to be ductile. 20.2 Mining subsidence effects
Bridge structures in areas underlain by known mineral deposits shall be designed to cater for anticipated mining subsidence effects. Mining subsidence effects may include— (a)
a vertical displacement;
(b)
change in the slope of the ground; or
(c)
the development of surface strains.
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Mining subsidence effects shall be included in the SLS checks of the superstructure, bearings, deck joints and substructure using a load factor of 1.0. The foundations shall be designed for mining subsidence effects at ULSs. For sites where accurate records and information are available a load factor of 1.5 shall be used. For all other sites, a load factor of 2.0 shall be used. 21 FORCES FROM BEARINGS
Bridges shall be designed for the forces arising from the friction of sliding and rolling bearings, and the load-displacement characteristics of elastomeric bearings. The forces due to friction on bearings shall be calculated considering permanent loads only acting. Characteristic values of the coefficient of friction, under normal operating conditions of bearings, shall be as specified in AS 5100.4. For ULSs, the design friction force shall be calculated using the characteristic coefficient of friction and the nominal dead loads of the structure.
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A load factor of 1.3 shall be used for the ULS. For SLSs, the average design friction forces, calculated using the characteristic coefficient of friction and the nominal dead loads of the structure shall be treated as a permanent effect, acting in either direction. A load factor of 1.0 shall be used for the SLS. The coefficient of friction of any surface intended for sliding to accommodate movements of a structure shall be taken as zero as one of the ULSs. The effects of a seized bearing in conjunction with permanent loads and thermal movements shall be considered. 22 CONSTRUCTION FORCES AND EFFECTS 22.1 General
The permanent forces and effects introduced during construction shall be considered in the design. Allowance shall also be made for the weight of any falsework or plant that may be carried by the structure, resulting from the anticipated method or sequence of construction. Forces arising during construction and the stability and serviceability of the component parts shall be considered in the design. Where the design is dependent on a particular method of construction, the structure shall be capable of safely sustaining all construction loads, and these constraints, inherent in the design, shall be clearly detailed in the drawings and specifications. The ability of bridge-supporting members to withstand the effects of flood and wind forces occurring during construction shall also be considered. Time-related relaxation of construction effects shall be considered where appropriate. The load factors to be applied in calculating the construction dead loads shall be as given in Table 22.1.
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TABLE 22.1 LOAD FACTORS FOR CONSTRUCTION DEAD LOADS ( g ) Type of construction
Type of material
ULSs where dead load Reduces safety
Increases safety
SLSs
Steel
1.1
0.9
1.0
Concrete
1.2
0.85
1.0
(b) Balanced cantilever structures At a section subjected to approximately equal favourable and unfavourable dead loads
All
1.1
1.0
1.0
(c) Anchor cantilever structures At a section subjected to unequal favourable and unfavourable dead loads
All
1.2
1.0
1.0
(d) Launched structures
All
1.2
0.85
1.0
(a) All, except for Items (b), (c) and (d)
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NOTES: 1
For large segmental cantilever and launched construction, where appropriate control and monitoring are exercised over dimensions, the relevant authority may approve a reduction of g to not less than 1.1 for ULSs, for the case where the dead load reduces safety.
2
The load factors shall be applied at a section where the member is subject to approximately equal favourable and unfavourable dead loads. This may occur during the construction phase of a structure built by the balanced cantilevering method. Where the completed structure is changed from the balanced cantilever state (e.g. into a continuous structure after closure), the load factors for non-balanced cantilever structures shall apply.
22.2 Minimum construction design loads 22.2.1 All bridges
The minimum construction design loads and load factors shall be in accordance with Table 22.2.1 except for the launching phase of an incrementally launched prestressed concrete bridge.
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TABLE 22.2.1 MINIMUM CONSTRUCTION DESIGN LOADS AND LOAD FACTORS FOR ALL BRIDGES (EXCEPT FOR THE LAUNCHING PHASE OF AN INCREMENTALLY LAUNCHED PRESTRESSED CONCRETE BRIDGE) Loading
Value
Dead load
As per Clause 6
Construction live load
0.5 kPa on all deck surfaces (minimum). The designer may specify a higher value.
Ultimate load factor See Table 22.1 1.8
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Small span components such as formwork over Super T voids shall be designed for a minimum of 5 kPa (representing over-thickness in concrete while placing). Differential temperature
90% of Clause 18.3 values
1.1
Wind load
The return interval for the design wind during construction shall be determined by the following equation:
1.0
R = 100N where R is the return period and N is the duration of construction in years. The minimum value of N is 2 years (see Note 1). Differential settlement and construction tolerance allowances between bearing levels
As specified in design (see Note 2).
1.0
NOTES: 1
During construction, various elements of the bridge may be more susceptible to wind loads than when the bridge is completed.
2
Differential settlement shall be monitored and controlled during construction.
22.2.2 Launching phase of an incrementally launched prestressed concrete bridges
The minimum construction design loads and load factors for the launching phase of an incrementally launched prestressed concrete bridge shall be in accordance with Table 22.2.2. The criteria for other types of bridge construction shall be subject to approval of the appropriate relevant authority.
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TABLE 22.2.2 MINIMUM CONSTRUCTION DESIGN LOADS AND LOAD FACTORS FOR THE LAUNCHING PHASE OF AN INCREMENTALLY LAUNCHED PRESTRESSED CONCRETE BRIDGE Loading
Value
Ultimate load factor
Dead load
As per Clause 6
See Table 22.1
Launching live load
0.5 kPa on all deck surfaces (minimum)
1.8
Differential temperature
As per Clause 18.3
0.9
Wind load
See Clause 17 (see Note 1)
0.7
Differential settlement and construction tolerance allowances between bearing levels
As specified in design (see Note 2)
1.0
NOTES: 1
Launching should not be carried out in strong wind (wind speed greater than 15 m/s).
2
Differential settlement shall be monitored and controlled during construction.
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22.3 Temporary structures
Temporary structures shall be designed in accordance with the relevant Standards and shall comply with relevant legislation and regulations. 23 LOAD COMBINATIONS 23.1 Classification of loads and load effects 23.1.1 General
Loads and load effects are divided into permanent effects (Clause 23.1.2), thermal effects (Clause 23.1.3), and transient effects (Clause 23.1.4). 23.1.2 Permanent effects (PE)
Permanent effects shall include the following: (a)
Structure dead load.
(b)
Additional permanent loads (superimposed dead load and rail ballast and track load).
(c)
Soil and groundwater loads.
(d)
Water flow forces and buoyancy corresponding to mean water level.
(e)
Shrinkage and creep effects (zero effects and full effects).
(f)
Prestress effects (before and after losses) (see Clause 19.2).
(g)
Differential movement of supports.
(h)
Forces from bearings.
23.1.3 Thermal effects
Thermal effects shall include the following: (a)
Effects due to variation in average bridge temperature.
(b)
Differential temperature effects.
The effects due to variation in average bridge temperature and due to differential temperature shall be combined to form the thermal effects load case.
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23.1.4 Transient effects
Transient effects shall include the following: (a)
Road and/or rail traffic loads, including dynamic effects.
(b)
Pedestrian, cyclist path and maintenance traffic loads.
(c)
Minimum restraint load.
(d)
Collision loads.
(e)
Road traffic barrier design loads.
(f)
Earth pressure from traffic loads.
(g)
Earthquake effects.
(h)
Water flow forces including forces due to moving objects and buoyancy.
(i)
Wind loads.
(j)
Fire effects.
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23.2 Minimum strength and stability
To ensure that the bridge satisfies minimum strength and stability criteria, the ultimate load combination of dead load + superimposed dead load + rail ballast and track load + soil and groundwater load shall be considered with load factors of— (a)
1.0 for groundwater; and
(b)
1.35 for effects that reduce safety and 0.9 for effects that increase safety for dead load, superimposed dead load, rail ballast and track load, and soil load.
23.3 ULS load combinations
Structures shall be designed for the worst permanent effects (PE) added to any of the thermal and transient effects as applicable. NOTE: Table D3, Appendix D, summarizes the load factors for load combinations.
The ULS load combinations to be considered for ultimate analysis shall include the following: (a)
Minimum strength and stability (Clause 23.2).
(b)
PE + road/rail traffic loads.
(c)
PE + pedestrian, cyclist path and maintenance traffic loads.
(d)
PE + minimum restraint load.
(e)
PE + collision load.
(f)
PE + road traffic barrier load.
(g)
PE + earth pressure from traffic load.
(h)
PE + earthquake effects.
(i)
PE + water flow forces.
(j)
PE + wind load.
(k)
PE + thermal effects
(l)
PE + fire effects.
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For PE + road/rail traffic loads [Item (b)], the wind load shall be included in the combination using a design wind speed of 35 m/s in all locations. For PE + collision load [Item (e)], the road/rail traffic loads shall be included in the combination with a load factor of 1.0 if they produce a more severe loading. For PE + water flow forces [Item (i)] and for PE + thermal effects [Item (k)], the road/rail traffic loads shall be included in these combinations with a load factor of 1.0 if they produce a more severe loading, unless it can be demonstrated that the structure will be closed to traffic under ultimate conditions. 23.4 SLS load combinations
At SLSs, more than one thermal effect and transient load can co-exist at any time. The basic combination to be considered for SLSs shall be as follows: PE (serviceability design load for one transient load or thermal effect)
k (serviceability design load for one or more other transient load or thermal effect) where
k = 0.7 for one additional effect
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= 0.5 for two additional effects The load factors to be applied to the SLS design loads shall be in accordance with the relevant clauses of this Standard. 24 ROAD SIGNS AND LIGHTING STRUCTURES 24.1 General
This Clause (24) sets out the requirements for the design of cantilever and portal sign structures and high-mast light poles. 24.2 ULS design
The ULS design wind speed shall be determined as follows: (a)
For structures defined in AS 5100.1 Clause 21.1, which present a risk of collapsing onto the road traffic lanes, the design wind speed shall be as specified in AS/NZS 1170.2 for a 1000 year average recurrence interval.
(b)
For structures defined in AS 5100.1 Clause 21.1, which do not present a risk of collapsing onto the road traffic lanes, the design wind speed shall be as specified in AS/NZS 1170.2 for a 200 year average recurrence interval.
The design wind pressure shall be as specified for hoardings in AS/NZS 1170.2, based on the wind speeds specified above. 24.3 SLS design 24.3.1 SLS design wind speed
The SLS design wind speed shall be as specified in AS/NZS 1170.2 for a 20-year average recurrence interval. 24.3.2 Portal sign structures
Portal sign structures shall be designed, fabricated and erected so that for the completed sign structure (including signs), the maximum deviation of the transverse member(s) under the action of self-weight only shall comply with the following tolerances: (a)
Downwards deviation from a straight line between the columns ............................... 0.
(b)
Upwards deviation from a straight line between the columns ....................... span/200.
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24.3.3 Cantilever sign structures
Cantilever sign structures shall meet the following requirements: (a)
The completed structure shall comprise a vertical column with a cantilever arm that is horizontal, subject to compliance with the minimum clearance requirements of the relevant authority and as required by the design (this geometry is termed the required profile). For cantilever sign structures, an assessment of the creep deflection due to foundation rotation shall be made. The required profile shall be adjusted to include the following presets: (i)
Vertical members Away from carriageway—Assessed creep but not less than 25 mm at the top of the vertical member.
(ii)
Horizontal members Upwards—Assessed creep but not less than 25 mm at the tip of the cantilever arm.
The required profile shall be defined on the drawings for all cantilever sign structures.
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(b)
Cantilever sign structures shall be designed, fabricated and erected so that for the completed sign structure (including signs) under the action of self-weight only, the maximum deviation from the required profile shall comply with the following tolerances: (i)
Vertical members: (A)
Towards carriageway ............................................................................ 0.
(B)
Away from carriageway .................................................................. H/200 (where H is the height from the base to the intersection of the uppermost principal horizontal members).
(ii)
Horizontal members: (A)
Downwards deviation ............................................................................ 0.
(B)
Upwards deviation .......................................................................... L/200 (where L is the length from the intersection of the principal members to the tip of the cantilever arm).
(c)
Cantilever sign structures shall be designed, fabricated and erected so that for the completed sign structure (including signs) under the action of serviceability wind loading only, the maximum horizontal deflection at the centre of the sign shall not exceed 1/125 of the combined length of the post and arm.
NOTE: Cantilever sign structures experience deflections due to the self-weight of the cantileverarm and the sign-face and wind loading together with possible long-term creep deflection as a result of foundation movement. Unless compensatory action is taken, these deflections may be excessive leading to an undesirable appearance of the structure. In extreme cases, the structure may become unserviceable.
24.4 Fatigue limit state design
Fatigue limit state design shall be in accordance with the AASHTO publication Standard Specifications for Structural Supports for Highway Signs, Luminaires and Traffic Signals. All aspects of the fatigue design shall be based on the AASHTO publication, including drag coefficients, fatigue importance factors, fatigue stress categories and constant-amplitude fatigue limits. Sign structures or high-mast light poles that could fall onto marked traffic lanes shall be treated in accordance with AASHTO requirements for Fatigue Category I.
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For installation sites where detailed yearly mean wind speed data is available from the Bureau of Meteorology, that site value of the yearly mean wind speed shall be used in the fatigue calculations for natural wind gusts in, accordance with AASHTO publication Standard Specifications for Structural Supports for Highway Signs, Luminaires and Traffic Signals. The potential for a resonant response of the cantilever arm of cantilever sign structures to vortex shedding originating from the column shall be assessed, including designs in which steel box-sections are used for the principal members. 24.5 Service live load on walkways
In structures fitted with walkways or service platforms, or both, the design load shall be as specified in Clause 8.2. 25 NOISE BARRIERS AND PROTECTION SCREENS 25.1 General
Noise barriers and protection screens may be fixed to a structure or be stand alone. Where a noise barrier or protection screen is used as a pedestrian barrier, it shall be designed for the loading specified in Clause 12.5 or Clause 25.3, whichever gives the most severe effect. Accessed by CENTRAL QUEENSLAND UNIVERSITY on 06 Jun 2017 (Document currency not guaranteed when printed)
25.2 Design life
The design life for noise barriers and protection screens shall be 50 years or as approved by the relevant authority. Anchorages shall be designed for a design life of 100 years on bridges and 50 years for other applications. 25.3 Wind load on noise barriers and protection screens 25.3.1 General
Wind pressures on noise barriers shall be determined in accordance with AS/NZS 1170.2 and subject to the requirements of this Clause. 25.3.2 Average recurrence interval (ARI)
The average recurrence interval (ARI) to be used for the calculation of the ULS wind forces for design shall be as follows, subject to approval of the relevant authority: (a)
200 years for noise barriers and protection screens that are located on road or rail authority property and cannot fall onto or slide down a slope onto other property, roadway, walkway or onto traffic areas.
(b)
1000 years for noise barriers that can fall onto railways and onto roadways.
(c)
500 years for all other noise barriers.
25.3.3 Change in terrain category
Any foreseeable change in terrain category shall be taken into consideration in accordance with AS/NZS 1170.2. 25.3.4 Shielding multiplier (Ms)
The shielding multiplier (Ms) specified in AS/NZS 1170.2 shall be taken as 1.0. 25.3.5 Topographic multiplier
AS/NZS 1170.2 accounts for sites in relation to the topographic features of hills, ridges and escarpments. Where the topography along a length of noise barriers varies, each situation shall be assessed taking into account its location relative to the prevailing topographic feature.
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Road embankments shall be treated as hills or escarpments. A road embankment shall be treated as an escarpment provided it meets the requirements for an escarpment and, additionally, the top width of the embankment is not less than the greater of— (a)
5 times the upwind height of the embankment; and
(b)
5 times the height of the upwind noise barrier.
25.3.6 Net pressure for hoardings and freestanding walls
The pressure coefficient shall be determined in accordance with AS/NZS 1170.2. Noise barriers on bridges shall be treated as hoardings. Other noise barriers shall be treated as freestanding walls. Where gates and gaps occur in the noise barrier, the barrier adjacent to the gap or gate shall be treated as a free end. 25.3.7 Free ends
Special consideration shall be given to the design of free ends. 25.3.8 Serviceability design
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The horizontal deflection of the panel under serviceability wind shall be limited to: span of panel 60
25.4 Robustness design loads 25.4.1 Protection screens
A protection screen shall be designed to withstand an ULS load of 2 kN applied over an area of 50 mm 50 mm on the screen, at any point, which produces the most adverse effect or as specified by the relevant authority. 25.4.2 Noise barriers
Unless approved otherwise by the relevant authority, noise barriers shall be capable of withstanding the impact of a 4 kg steel ball dropped from a height of 3 m when the panel is supported horizontally above the ground. The test panel shall be set up such that its ends are supported with a similar edge distance to that used in service. The test panel shall be set up for the worst case of span and width to be used in service. The impact shall cause only superficial scratches and marks on the panel. A depth deformation of 4 mm within a circle of 20 mm diameter shall be deemed acceptable. Glass panels shall not crack or shatter. 26 FIRE EFFECTS
Where the relevant authority specifies that a bridge shall be designed for the effects of fire, time-temperature curves for the fire shall be— (a)
as specified by the relevant authority;
(b)
interpolated from test data from fire tests that replicate the chosen fire conditions;
(c)
determined by fire models and engineering judgement where appropriate test data does not exist;
(d)
taken from AS 1530.4 for cellulose materials; or
(e)
as prescribed in Table 26.
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TABLE 26 DESIGN TIME-TEMPERATURE CURVES FOR FIRE Structural elements Traffic type
Hydrocarbon fire curve RWS/HCinc
Rail
RABT-ZTV
Bus
RABT-ZTV
120
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Road
Duration minutes
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APPENDIX A
DESIGN LOADS FOR SPECIAL PERFORMANCE LEVEL BARRIERS (Informative) A1 SCOPE
This Appendix provides typical ultimate design loads and load distribution lengths and effective heights for special performance level barriers. A2 DESIGN LOADS FOR SPECIAL PERFORMANCE LEVEL BARRIERS
For special performance level barriers, the loads and distribution lengths given in Table A2 may be used. For other special performance level barriers, the specification of the relevant authority applies. TABLE A2 Accessed by CENTRAL QUEENSLAND UNIVERSITY on 06 Jun 2017 (Document currency not guaranteed when printed)
DESIGN LOAD FOR SPECIAL PERFORMANCE LEVEL BARRIERS
Barrier performance level
Test level 6 (36 t articulated tanker) Greater than test level 6 (44 t articulated van)
Ultimate transverse outward load (F T )
Ultimate longitudinal or transverse inward load (F L )
Vehicle contact length for transverse load (L T ) and longitudinal load (L L )
Ultimate vertical downward load (F V )
Vehicle contact length for vertical load (L V )
kN
kN
m
kN
m
750
250
2.4
375
12.0
1200
400
2.5
600
15.0
A3 EFFECTIVE HEIGHTS
The minimum effective heights given in Table A3 may be adopted for the special performance level barriers unless the relevant authority specifies that other values are appropriate. TABLE A3 MINIMUM EFFECTIVE HEIGHT OF TRAFFIC BARRIER Barrier performance level
Minimum effective height mm
Special ( TL6–44 t articulated T44 van)
1500
Special (TL6–36 t articulated tanker)
1800
Special—Other
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To be specified by the relevant authority
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APPENDIX B
DISPLACEMENT-BASED EARTHQUAKE DESIGN (Informative) B1 GENERAL
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The informative provisions for earthquake design in this Appendix are applicable to bridges that include the following: (a)
Conventional superstructure and support types, such as slab, beam and slab, boxgirder and truss bridges supported on single- or multi-column piers and/or abutments.
(b)
Spans not greater than 100 m.
(c)
Angular change of the direction of the longitudinal axis of the bridge between abutments less than 90°.
(d)
Skew angles less than 35°.
(e)
Maximum pier height of 40 m.
(f)
Maximum characteristic concrete compressive strength of 65 MPa in bridge substructures, except that for bridge piers with characteristic concrete compressive strength higher than 65 MPa, design for earthquake load cases has to be carried out assuming characteristic concrete compressive strength of 65 MPa for the piers, and using the confinement details for high strength concrete in accordance with AS 5100.5.
For other bridges, or for bridges where seismic base isolation is to be implemented, specialist advice has to be sought for the assessment of earthquake effects. The effects of excessive settlement of approach embankments and the increased earth pressure on abutments has to be considered in the design for earthquake effects. The possibility of soil liquefaction has to be investigated where saturated sandy and silty soils within 10 m of the ground surface have a standard penetration test (SPT) value of 10 or less. The earthquake effects calculated in accordance with this Appendix are to be considered as design effects at the ULS for member strengths, overall stability of both the structure and its components, and horizontal movements. As an alternative to the displacement-based design procedure set out in this Appendix, for a specific structure that is first mode dominant a displacement-based design may be undertaken using a non-linear static pushover analysis, subject to approval of the relevant authority. When undertaking such an analysis the seismic demand has to be based on a response spectrum defined by 1.5kpZCh (T). B2 DISPLACEMENT-BASED PRINCIPLES B2.1 Analysis principles
Design actions in the displacement-based design method are expressed in terms of the seismic displacement demand, which depends on the bridge earthquake design category and design performance level, the probability factor, the hazard factor, the site subsoil class, and the fundamental natural period and damping of the structure. Bridge piers have to be designed to have a horizontal displacement capacity (see Paragraph B10) that equals or exceeds the seismic displacement demand under the design earthquake (see Paragraph B9).
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The bridge has to be subdivided longitudinally into bridge frames between expansion joints and abutments. For longitudinal earthquake response, each bridge frame has to be considered separately (stand-alone analysis) and the results compared with a further analysis where all joints are considered to be fully closed. For transverse response, each bridge frame has to be considered separately, with the mass and stiffness of adjacent bridge frames modelled at the movement joint where the fundamental natural period of the adjacent bridge frame differs by more than 25% from that of the bridge frame under consideration. Where Paragraph B4 stipulates analysis of vertical earthquake response, a span-by-span static analysis may be used, provided the span under consideration is modelled together with adjacent continuous spans, if any, at either end of the span. End support conditions at the far end of the adjacent span are to be considered fixed if continuous over the support, or pinned as appropriate (e.g. if the end of the adjacent span is simply supported at an abutment).
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The fundamental natural period of vibration of each bridge frame in the longitudinal direction (i.e. span direction), the transverse direction and (where required) the vertical direction have to be determined using acceptable methods of structural analysis, or from the appropriate equations in this Appendix. Reinforced concrete superstructure members have to be modelled using the effective cracked-section stiffness. Prestressed concrete superstructure members have to be modelled using the gross-section stiffness. The longitudinal and transverse stiffness of piers are to include the influence of foundation and bearing flexibility, where appropriate. Elastically responding piers (i.e. within the yield displacement capacity) are to be modelled using the effective cracked-section stiffness. Piers designed for a ductile response are to be modelled using effective cracked-section stiffness divided by d , where d is the displacement ductility defined in Paragraph B12.10. Bridge members need to have sufficient flexural and shear strength (capacity) to avoid unintended plastic hinges and brittle (shear) failure, as described in Paragraph B15. The earthquake action effects (e.g. moment and shear forces) are to be determined from horizontal forces associated with the seismic displacement demand. Acceptable methods of structural analysis will need to be used. When a bridge is designed for earthquake effects using displacement-based design principles, and the seismic displacement demand of any part of the bridge exceeds the yield displacement capacity of that part, then the bridge has to be designed for a ductile response (Paragraph B12). Designing for a ductile response is referred to as ductile earthquake design. Not all bridges will require ductile earthquake design. It will be possible, using the provisions of this Standard, to show that some bridges designed for permanent and traffic load will respond elastically to the design level of seismicity, without the need for ductile earthquake design. Where ductile earthquake design is required, the following apply: (a)
A clearly defined collapse mechanism to be established.
(b)
The structural members to be ductile at the potential plastic hinge locations defined in the collapse mechanism.
(c)
Structural analysis to account for the ductile behaviour of the bridge members following yielding under the effects of the design earthquake.
(d)
Properties that are affected by the ductile response, including increased damping, reduced stiffness and increased fundamental natural period of the bridge, to be taken into consideration.
(e)
The minimum detailing criteria given in Paragraph B17 to ensure that the required ductility at potential plastic hinges can be achieved.
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B2.2 Seismic mass distribution
As a minimum representation of the seismic mass distribution, the tributary superstructure mass (including mass of dead load and mass of superimposed dead load), pier headstock mass, and tributary mass of pier columns have to be combined as a single mass acting in the plane of the pier, and at the resultant height of the combined masses. In this context, the tributary mass of the pier columns may be taken as 33% of the total pier column mass, positioned at the top of the pier column. For bridges with tall piers of significant mass, particularly those in the height range of 20 m to 30 m, the influence of pier inertia on the earthquake response of the pier responding as a vertical beam will need to be considered. The pier mass distribution has to be represented by at least four masses along the pier height. Where analysis of vertical earthquake response is stipulated by Paragraph B4, or for the analysis of horizontal earthquake response for bridges with spans longer than 40 m with significant transverse flexibility of superstructure, the superstructure mass of the span under consideration and of the adjacent spans, if any, have to be distributed to not less than four locations along the span.
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Where the superstructure is supported on bearings whose flexibility in the direction considered is such that superstructure displacements are expected to exceed pier headstock displacements by at least 200%, pier headstock mass and pier mass may be ignored. B3 DISPLACEMENT-BASED DESIGN PROCEDURE
Design has to be undertaken for horizontal earthquake effects in both the longitudinal direction (i.e. span direction) and the transverse direction of the bridge. Design has to be undertaken for vertical earthquake effects where stipulated by Paragraph B4. The procedure is summarized as follows: (a)
Determine the bridge earthquake design category and design performance level (Paragraphs B4 and B5).
(b)
Determine the probability factor and the hazard factor (Paragraph B6).
(c)
Determine the site subsoil class and hence the elastic seismic displacement spectral shape factor (Paragraphs B7 and B8).
(d)
Determine the corner-period elastic seismic displacement demand for horizontal earthquake response (Paragraph B9.1) in the direction considered (longitudinal or transverse).
(e)
Determine the yield displacement capacity of each pier (Paragraph B10.1) in the direction considered (longitudinal or transverse).
(f)
For each pier, check if the pier yield displacement capacity exceeds the corner-period elastic seismic displacement demand for horizontal earthquake response (Paragraph B11.2(a) or B11.3(a) as appropriate) in the direction considered (longitudinal or transverse). If so, the pier will remain elastic under the design earthquake and ductile earthquake design is not required.
(g)
If the check in Step (f) fails, determine the fundamental natural period of the bridge in the direction considered (longitudinal or transverse).
(h)
Determine the elastic seismic displacement demand for horizontal earthquake response at the fundamental natural period, and check if the pier yield displacement capacity exceeds this displacement demand (see Paragraph B11.2(b) or B11.3(b) as appropriate). If so, the pier will remain elastic under the design earthquake and ductile earthquake design is not required.
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(i)
If the yield displacement capacity is less than the elastic seismic displacement demand for horizontal earthquake response at the fundamental natural period, plastic hinges will be expected to form and ductile earthquake design is required. The ductile seismic displacement demand for horizontal earthquake response will need to be determined (Paragraph B9.2) and ductile earthquake design will need to be carried out to determine the earthquake forces (Paragraph B12).
(j)
If the check in Step (i) identifies that plastic hinges will be expected to form, account for the P- effect (Paragraph B14), and verify the static analysis results using dynamic analysis if stipulated by Paragraph B4.
(k)
Where stipulated by Paragraph B4, determine the elastic seismic displacement demand for vertical earthquake response.
(l)
Determine the required design strength (capacity) of bridge members (Paragraph B15), determine the abutment forces (Paragraph B16), and provide detailing requirement for the design ductility level (Paragraph B17).
B4 BRIDGE EARTHQUAKE DESIGN CATEGORIES (BEDC) AND ANALYSIS REQUIREMENTS
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B4.1 BEDC classification
Bridges and associated structures, such as approach retaining walls, will be classified by the relevant authority; if not classified by the relevant authority the following classification applies: (a)
BEDC-4 Bridges and associated structures that are essential to post-earthquake recovery, as specified by the relevant authority, and major bridges whose operation is essential to economic viability at state or national levels.
(b)
BEDC-3 Bridges that are designed to carry high volumes of road, rail or pedestrian traffic, or bridges over other high traffic volume roadways, railways or buildings.
(c)
BEDC-2 Minor bridges of two or more spans, and not covered by BEDC-3 or BEDC-4.
(d)
BEDC-1 Minor single span bridges carrying infrequent traffic, and not covered by BEDC-2, 3, or 4.
In situations where a bridge spans a road and/or rail of a higher category, the higher category has to be adopted for the bridge design. B4.2 Requirements for BEDC-1
Bridge structures in BEDC-1 need not be analysed for earthquake forces. The minimum lateral restraint provisions of Clause 10 of this Standard will apply. The minimum bearing seat width measured normal to the face of an abutment or pier has to be 0.3 m. B4.3 Requirements for BEDC-2
Where Paragraph B11 stipulates ductile earthquake design for bridge structures in BEDC-2, the effects of earthquake actions have to be determined using the procedure defined in Paragraph B12. For all bridges in BEDC-2, vertical earthquake effects need not be considered. Abutment forces have to be determined using the procedure in Paragraph B16. The detailing of structural members, restraining devices, bearings and deck joints has to be in accordance with Paragraph B17.
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B4.4 Requirements for BEDC-3
Where Paragraph B11 stipulates ductile earthquake design for bridge structures in BEDC-3, the effects of earthquake actions have to be determined using the procedure defined in Paragraph B12. NOTE: The final design of bridge structures with significant irregularity in structural form should be verified by dynamic analysis in accordance with either a modal-response-spectrum analysis, using effective member stiffness and system damping at expected maximum displacement demand, or an inelastic time-history analysis in accordance with AS 1170.4.
For all bridge structures in BEDC-3, the effects of both horizontal and vertical earthquake actions, and the P- effects have to be considered. Abutment forces have to be determined in accordance with Paragraph B16. The detailing of structural members, restraining devices, bearings and deck joints has to be in accordance with Paragraph B17. B4.5 Requirements for BEDC-4
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Where Paragraph B11 stipulates ductile earthquake design for bridge structures in BEDC-4, the effects of earthquake actions have to be determined using the procedure defined in Paragraph B12. In addition, the final design has to be verified by dynamic analysis in accordance with either a modal-response-spectrum analysis, using effective member stiffness and system damping at expected maximum seismic displacement demand, or an inelastic time-history analysis in accordance with AS 1170.4. For all bridge structures in BEDC-4, the effects of both horizontal and vertical earthquake actions, and the P- effects have to be considered. Abutment forces have to be determined using the procedure in Paragraph B16. The detailing of structural members, restraining devices, bearings and deck joints have to be in accordance with Paragraph B17. B5 DESIGN PERFORMANCE LEVEL
The strength and serviceability design of bridges has to be calculated based on the seismic displacement demand at either the damage control performance level or the service (immediate use) performance level. After the occurrence of the design earthquake, a bridge designed for the damage control performance level should retain its structural integrity. Parts of the bridge susceptible to damage by their contribution to energy dissipation during the design earthquake have to be designed in such a manner that the structure can sustain the actions resulting from use by emergency traffic, and that inspection/repairs can be performed. After the occurrence of the design earthquake, bridges designed for the service (immediate use) performance level should be able to be used immediately by vehicles and plant for disaster recovery operations and evacuation of the populace. There should be no need to reduce ordinary traffic over the bridge, or to carry out immediate repairs. Bridges have to be designed for the damage control performance level under the design earthquake. BEDC-4 bridges have to be designed for the service (immediate use) performance level under the design earthquake. B6 PROBABILIY FACTOR (k p) AND HAZARD FACTOR (Z)
Bridges have to be designed for an annual probability of exceedance in accordance with Table B6. The probability factor kp has to be determined from the annual probability of exceedance in accordance with AS 1170.4. Unless determined by a site-specific seismology study, the hazard factor Z has to be determined in accordance with AS 1170.4, but to be not less than 0.08. Standards Australia
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TABLE B6 ANNUAL PROBABILITY OF EXCEEDANCE BEDC
Annual probability of exceedance (P)
4
1/2000
3
1/1000
2
1/500
1
Not applicable
B7 SITE SUBSOIL CLASS
Determine the site subsoil class in accordance with AS 1170.4. For bridges with pilesupported foundations, the site subsoil class has to be based on the upper layers of the soil profile.
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B8 ELASTIC SEISMIC DISPLACEMENT SPECTRAL SHAPE FACTOR [ h(T)]
The period-dependent elastic seismic displacement spectral shape factor [ h (T)] will depend on the site subsoil class in accordance with Paragraph B7, unless determined by an approved site-specific seismology study. When site-specific seismology studies defining the displacement spectrum shape are not available, the seismic displacement spectral shape factor has to be calculated using the following equation:
h(T)
gT 2 = Ch T 4 2
g
= acceleration due to gravity, in metres per second squared
T
= period of vibration, in seconds, or 1.5 s, whichever is the lesser
Ch(T)
= acceleration spectral shape factor as a function of period, given in Table 6.4 of AS 1170.4—2007
. . . B8
where
The seismic displacement spectral shape factors for different subsoil classes resulting from Equation B8 are listed in Table B8 and are plotted in Figure B8.
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TABLE B8
Period seconds
Ae Strong rock
Be Rock
Ce Shallow soil
De Deep or soft soil
Ee Very soft soil
0
0
0
0
0
0
0.1
6
7
9
9
9
0.2
23
29
37
37
37
0.3
52
66
82
82
82
0.4
70
87
124
146
146
0.5
87
109
155
229
229
0.6
105
131
186
295
329
0.7
122
153
217
344
448
0.8
140
175
248
394
585
0.9
157
197
280
443
689
1
175
219
311
492
765
1.2
210
262
373
590
918
1.5
262
328
466
738
1148
1.7
262
328
466
738
1148
2
262
328
466
738
1148
2.5
262
328
466
738
1148
3
262
328
466
738
1148
DISPL ACEM ENT, m m
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ELASTIC SEISMIC DISPLACEMENT SPECTRAL SHAPE FACTORS [ h(T)], mm
120 0
Soil E e
800
Soil D e
Soil C e 400
Soil B e Soil A e
0 0
1
2
3
PERIO D, s e c o n d s
FIGURE B8 ELASTIC SEISMIC DISPLACEMENT SPECTRAL SHAPE FACTORS [Δ h(T)] FOR DIFFERENT SUBSOIL CLASSES
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B9 SEISMIC DISPLACEMENT DEMAND FOR EARTHQUAKE RESPONSE B9.1 Elastic seismic displacement demand for horizontal earthquake response
Determine elastic seismic displacement demand for horizontal earthquake response [Δe(T)] using the following equation: Δe(T)
= kpZΔh(T)
T
= period of vibration
kp
= probability factor, given in Paragraph B6
Z
= hazard factor, given in Paragraph B6
. . . B9.1
where
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Δh(T)
elastic seismic displacement spectral shape factor at period T, given in Paragraph B8
The elastic seismic displacement demand [Δ e(T)] calculated from Equation B9.1 represents the elastic response of bridges in the longitudinal direction. It represents the elastic response in the transverse direction for uniform bridges only, which are bridges for which the transverse displacements at the top of every pier and abutment may be considered to be equal (e.g. bridges with uniform transverse stiffness and mass). For the elastic response of non-uniform bridges in the transverse direction, the seismic displacement demand of piers will vary according to the transverse mode shape. Calculate the elastic seismic displacement demand of non-uniform bridges in accordance with Paragraph B11.3. The corner-period of the elastic seismic displacement spectral shape factor equals 1.5 s (see Figure B8) and corresponds to the maximum elastic seismic displacement demand. Calculate the corner-period elastic seismic displacement demand [Δe(1.5)] from Equation B9.1 at a period of vibration of 1.5 s. B9.2 Ductile seismic displacement demand for horizontal earthquake response
Calculate the seismic displacement demand [Δ d (T)] for ductile response by multiplying the elastic seismic displacement demand given by Equation B9.1 by a damping modifier [R], as follows: Δd(T)
= RΔe(T) = RkpZΔh(T)
R
= damping modifier
. . . B9.2(1)
where
0.07 = 0.02 e
0.5
. . . B9.2(2)
where
e
= bridge frame equivalent viscous damping ratio corresponding to the design ductility level of response, given in Paragraph B12.7
The seismic displacement demand [Δ d (T)] calculated from Equation B9.2(1) represents the ductile response of bridges in the longitudinal direction. It represents the ductile response in the transverse direction for uniform bridges only, which are bridges for which the transverse displacements at the top of every pier and abutment may be considered to be equal (e.g. bridges with uniform transverse stiffness and mass). For the ductile response of non-uniform bridges in the transverse direction, the seismic displacement demand of piers will vary according to the transverse mode shape. Calculate the ductile seismic displacement demand of non-uniform bridges in accordance with Paragraph B11.3.
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B9.3 Elastic seismic displacement demand for vertical earthquake response
For periods less than or equal to 1.0 s, the elastic seismic displacement demand for vertical earthquake response (upwards and downwards) are to be taken as equal to two thirds of the elastic seismic displacement demand for horizontal response given by Equation B9.1. For periods greater than 1.0 second, the elastic seismic displacement demand for vertical earthquake response is to be taken as equal to two thirds of the horizontal value at a period of 1.0 second. B10 PIER DISPLACEMENT CAPACITY B10.1 Yield displacement capacity of piers
The yield displacement capacity of a pier (δy) will depend on the yield curvature and the end fixity conditions at the base and top. For prismatic piers, it may be expressed as follows:
δy
= C1 ϕy(H + Lsp )2 + δf + δb
C1
= coefficient dependent on the end fixity conditions, in the direction of displacement being considered
. . . B10.1(1)
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where
In the absence of more detailed analysis, C1 may be taken as 1/3 for piers considered fixed against rotation at the base and free to rotate at the top (for the direction of displacement being considered) and C1 may be taken as 1/6 for piers considered fixed against rotation at the base and at the top (for the direction of displacement being considered).
H
= pier height between the centre of plastic hinges at the top and bottom of the pier in double bending; or pier height from the centre of the plastic hinge to the point of contraflexure at top or bottom of the pier in single bending, in metres
δf
= displacement capacity deformation, in metres
δb
= displacement capacity at superstructure resulting from the pier-cap bearing deformation, in metres
Lsp
= strain penetration length for reinforced concrete piers, given by Equation B10.1(2), in metres
at
superstructure
resulting
from
= 0.022 fsyedbl
foundation
. . . B10.1(2)
where
fsye
= expected yield strength of Table B15.2), in megapascals
dbl
= diameter of longitudinal reinforcement steel, in millimetres
ϕy
= yield curvature, which may be approximated for piers of simple prismatic shape by Equation B10.1(3), in 1/metre
flexural
reinforcement
(see
Column 2
For piers with non-prismatic or complex prismatic section shapes, the yield curvature may be determined by finite-element analysis or other means recognizing the non-linear behaviour of materials and the influence of cracking, where appropriate, as follows:
ϕy
=
2.15 y Dc
, in 1/metre
. . . B10.1(3)
where
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εy
= strain at the expected yield strength of the flexural reinforcement (or structural steel) (see Column 2 of Table B15.2)
Dc
= section depth in the direction considered, in metres
B10.2 Ductile displacement capacity of piers B10.2.1 General
The ductile displacement capacity (δd ) has to be not less than the ductile seismic displacement demand (d ) calculated in accordance with Paragraph B9.2. The ductile displacement capacity of a pier (d ) equals the sum of the yield displacement capacity (δy) defined in Paragraph B10.1 and the additional inelastic displacement capacity (δp ) corresponding to the strain limit at the design performance level (see Paragraphs B10.2.2 and B10.2.3). The inelastic displacement capacity (δp ) depends on the plastic hinge length, the strain limits in the plastic hinge, and the pier height, and may be calculated using the following equation:
δp
= pH
p
= plastic rotation capacity at the plastic hinge, in radians, defined as
. . . B10.2.1(1)
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where (ϕls ϕy)Lp
. . . B10.2.1(2)
ϕls
= ductile curvature corresponding to the strain limit at the relevant design performance level in accordance with Paragraph B10.2.2 or Paragraph B10.2.3 as applicable, in 1/metre
ϕy
= yield curvature given in Equation B10.1(3), in 1/metre
H
= pier height between the centre of plastic hinges at the top and bottom of the pier in double bending, or pier height from the centre of the plastic hinge to the point of contraflexure at top or bottom of the pier in single bending, in metres
Lp
= plastic hinge length, in metres = kLc + Lsp 2Lsp
. . . B10.2.1(3)
Lsp
= strain penetration length, defined in Equation B10.1(2), in metres
Lc
= distance from the centre of the plastic hinge to the point of contraflexure in the pier, in metres
k
ul 1 0.08 = 0.2 f sy
ful
= characteristic ultimate strength of flexural reinforcement, in megapascals
fsy
= characteristic yield strength of flexural reinforcement, in megapascals
f
. . . B10.2.1(4)
B10.2.2 Strain limits for damage control performance level
The following strain limits apply: (a)
Reinforcing steel Tensile strain limit in flexural reinforcement (εsd ) in plastic hinges may be related to the volumetric ratio of lateral (transverse) reinforcement (ρs) in accordance with Equation B10.2.2(1). The tensile strain should not exceed 50% of the strain at maximum stress of the flexural reinforcement (εsul), where: εsd
= 0.015 + 6(ρs 0.005) 0.5εsul
. . . B10.2.2(1)
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where
(b)
ρs
= volumetric ratio of lateral (transverse) reinforcement
εsul
= strain at maximum stress of flexural reinforcement
Concrete compression Compressive strain limit of concrete (εcd) in plastic hinges may be related to the volumetric ratio of lateral reinforcement (ρs), provided the concrete compressive strain does not exceed the value given by the following equation:
s fsy.t sut
εcd
= 0.004 1.4
ρs
= volumetric ratio of lateral (transverse) reinforcement
f cc
. . . B10.2.2(2)
where
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f c εsut
= confined compressive strength of concrete, which may be taken as 1.5 f c if not calculated by rational analysis = characteristic yield strength of lateral reinforcement = characteristic compressive (cylinder) strength of concrete at 28 days = strain at maximum stress of lateral reinforcement
(c)
Structural steel Compressive and tensile strain in ductile structural steel piers to not exceed values corresponding to the onset of buckling under cyclic reversals of moment. In the absence of definitive design information, a value of εsd = 0.02 has to be assumed.
(d)
Hollow concrete piers The maximum concrete compressive strain for hollow reinforced or prestressed piers to not exceed the lesser of εcd given by Equation B10.2.2(2), or 0.006.
(e)
Prestressing steel Tensile strain in prestressing steel to not exceed the limit of proportionality strain.
B10.2.3 Strain limits for service (immediate use) performance level
The following apply: (a)
Reinforcing steel Tensile strain in reinforcing steel (εsd ) in plastic hinges to not exceed 0.015.
(b)
Concrete compressive strain Compressive strain of concrete εcd in plastic hinges to not exceed 0.004.
(c)
Structural steel strain Compressive and tensile strain in ductile structural steel piers εsd to not exceed 0.01.
(d)
Prestressing steel Tensile strain in prestressing steel to not exceed the limit of proportionality strain.
B10.3 Displacement capacity of a bridge frame in the transverse direction
The transverse displacement capacity of a bridge pier or abutment (δi) has to be related to the normalized fundamental mode shape and the displacement capacity of the first bridge frame pier or abutment to reach displacement capacity (δc), using the following equation:
i
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i = c c
. . . B10.3
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where
i
= value of normalized fundamental displacement mode shape at pier or abutment i
c
= value of normalized fundamental displacement mode shape at the first bridge frame pier or abutment to reach displacement capacity
c
= displacement capacity of the first bridge frame pier or abutment to reach displacement capacity
In Equation B10.3, the displacement capacities of inelastic structural elements should be based on the strain limits defined in Paragraph B10.2 and should include the effects of bearing and foundation flexibility, where appropriate. NOTE: Equation B10.3 may be also applied to calculate the seismic displacement demand of any pier in relation to the critical pier.
B11 CRITERIA FOR EXEMPTION FROM DUCTILE EARTHQUAKE DESIGN
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B11.1 General
The criteria for determining if bridge frames under longitudinal response, and bridge frames with uniform mass and stiffness distributions under transverse response, may be exempt from ductile earthquake design are given in Paragraph B11.2. The criteria for determining if bridge frames with non-uniform mass and stiffness distributions under transverse response may be exempt from ductile earthquake design are given in Paragraph B11.3. B11.2 Bridge frames under longitudinal response and bridge frames with uniform mass and stiffness distributions under transverse response
The following exemptions from ductile earthquake design apply: (a)
Yield displacement capacity (y) exceeds corner-period elastic seismic displacement demand ∆e(1.5) When the yield displacement capacity given by Equation B10.1(1) of all piers exceeds the elastic seismic displacement demand e given by Equation B9.1 for T = 1.5 s (the corner-period) the bridge frame may be exempt from ductile earthquake design in that direction.
(b)
Yield displacement capacity (y) exceeds the elastic seismic displacement demand for the bridge frame fundamental natural period in the direction considered ∆e(Tf) If the criterion defined by Paragraph B11.2(a) is not satisfied, calculate the bridge frame fundamental natural period in the direction considered (Tf). When the yield displacement capacity given by Equation B10.1(1) of all piers exceeds the elastic seismic displacement demand for the bridge frame fundamental natural period in the direction considered (Tf) given in Paragraph B9.1, the bridge frame may be exempt from ductile earthquake design in that direction.
The fundamental natural period Tf of bridge frames in the longitudinal direction, and of uniform bridge frames in the transverse direction, may be determined from the following equation: n
Tf
= 2
m i 1 n
i
Ki
. . . B11.2
i 1
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where mi
= one of the n individual masses representing the bridge frame, determined in accordance with Paragraph B2.2
Ki
= individual pier longitudinal or transverse stiffness, expressed as force per unit longitudinal or transverse displacement at the location of mass i
B11.3 Bridge frames with non-uniform mass and stiffness distributions
The following exemptions from ductile earthquake design apply: (a)
Yield displacement capacity (y) exceeds corner-period elastic seismic displacement demand Δe(1.5) When the yield displacement capacity given by Equation B10.1(1) of all piers exceeds the elastic seismic displacement demand (Δe) given by the following equation for T = 1.5 s (the corner-period), the bridge frame may be exempt from ductile earthquake design in that direction: Δe
= 1.1 e 1.5
i e
. . . B11.3(1)
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where Δe(1.5) = corner-period elastic seismic displacement demand for pier i given by Equation B9.1 for T = 1.5 s
i
= value of fundamental displacement mode shape at pier or abutment i
e
= characteristic value of normalized fundamental mode shape of the bridge frame, given by the following equation: n
m =
i 1 n
2 i i
. . . B11.3(2)
mii i 1
mi
(b)
= one of the n individual masses representing the bridge frame, determined in accordance with Paragraph B2.2
Yield displacement capacity (y) exceeds the elastic seismic displacement demand for the bridge frame fundamental natural period in the direction considered ∆y(Tf) If the criterion defined by Paragraph B11.3(a) is not satisfied, calculate the bridge frame fundamental natural period in the direction considered (Tf). When the yield displacement capacity given by Equation B10.1(1) of all piers exceeds the elastic seismic displacement demand (Δe) given by the following equation for the bridge frame fundamental natural period in the direction considered (Tf) the bridge frame may be exempt from ductile earthquake design in that direction:
Δe
= 1.1 e Tf
i e
. . . B11.3(3)
where
Standards Australia
Δe(Tf)
= elastic seismic displacement demand given by Equation B9.1 for the fundamental natural period in the direction considered
i
= value of fundamental displacement mode shape at pier or abutment i
e
= characteristic value of the fundamental mode shape of the bridge frame, given by Equation B11.3(2)
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The fundamental natural period (Tf) of the non-uniform bridge frame in the transverse direction may be determined from the following equation: n
Tf
= 2
m i
i 1
Fi
. . . B11.3(4)
n
F
i
i 1
where Fi
= design transverse force at bridge frame mass location mi proportional to m i i
ΔFi
= transverse displacement at bridge frame mass location mi due to the application of Fi
mi
= one of the n individual masses representing the bridge frame, determined in accordance with Paragraph B2.2
Alternatively, for bridges in BEDC-2 the Rayleigh equation may be used to estimate the fundamental natural period, as follows:
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n
Tf
= 2
m i 1 n
i
2 Fi
g mi Fi
. . . B11.3(5)
i 1
where g
= acceleration due to gravity
B12 DUCTILE EARTHQUAKE DESIGN OF BRIDGE FRAMES B12.1 Representation of a bridge frame as an equivalent single degree of freedom structure
Where Paragraph B11 does not provide an exemption from ductile earthquake design, determine the design horizontal earthquake force in accordance with the provisions of this Paragraph. Abutment design horizontal forces have to be calculated in accordance with Paragraph B16. B12.2 Design horizontal earthquake force from displacement-based design analysis
Calculate the horizontal earthquake force for a bridge frame (FF) using the following equation: FF
= keΔk
Δk
= characteristic horizontal seismic displacement demand of the bridge frame, calculated in accordance with Paragraph B12.3
ke
= equivalent effective stiffness of the bridge frame, calculated in accordance with Paragraph B12.4
. . . B12.2
where
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B12.3 Bridge frame characteristic horizontal seismic displacement demand in the transverse direction
Calculate the characteristic horizontal seismic displacement demand of the bridge frame in the transverse direction (Δk ) using the following equation: n
Δk
=
n
m m i 1
i
2 i
i 1
i
. . . B12.3
i
where Δi
= horizontal seismic displacement demand of bridge frame mass mi, given in Paragraph B11.3(b)
mi
= one of the n individual masses representing the bridge frame, determined in accordance with Paragraph B2.2
B12.4 Equivalent bridge frame stiffness
Calculate the equivalent bridge frame stiffness (ke ) using the following equation: ke
4 2 me = Te2
. . . B12.4
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where Te
= equivalent fundamental natural period of the bridge frame, defined in Paragraph B12.6
me
= effective mass of the bridge frame defined in Paragraph B12.5
B12.5 Bridge frame effective mass
Calculate the bridge frame effective mass (me) using the following equation: me
=
n
mi i
i 1
k
. . . B12.5
where Δk
= bridge frame characteristic horizontal seismic displacement demand, as defined by Equation B12.3
mi
= one of the n individual masses representing the bridge frame, determined in accordance with Paragraph B2.2
Δi
= horizontal seismic displacement demand of bridge frame mass mi, given in Paragraph B11.3(b)
B12.6 Bridge frame equivalent fundamental natural period
The equivalent fundamental natural period (Te) of the bridge frame is found from the ductile seismic displacement demand defined in Paragraph B9.2 corresponding to the calculated bridge frame equivalent viscous damping defined in Paragraph B12.7.
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B12.7 Bridge frame equivalent viscous damping ratio
The bridge frame equivalent viscous damping ratio ( e) is related to the seismic shear force at the top of each pier and abutment (Vi), the ductile seismic displacement demand at the top of each pier and abutment (Δi), and the elastic viscous damping ( i) of the structural components (including the superstructure, abutments and bearings where applicable) of the bridge frame as given in the following equation, which is applicable to the transverse and longitudinal directions: n
n
i 1
i 1
Vi ii Vi i
e
=
Vi
= seismic shear force at the top of pier or abutment component i
Δi
= ductile seismic displacement demand at the top of pier or abutment component i
i
= equivalent viscous damping of structural component i of the bridge frame given in Paragraph B12.8
. . . B12.7(1)
where
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Damping of piers with flexible foundations and bearings may be calculated using the following equation:
p
=
b b f f s s b f s
. . . B12.7(2)
where Δb , Δf, Δs = bearing, foundation and pier structural displacement, respectively
b , f, s
= bearing, foundation and pier structural damping, respectively
B12.8 Equivalent viscous damping ratio of component actions
The equations for calculating the equivalent viscous damping ratio given in this Paragraph allow for elastic and hysteretic damping. The following apply Paragraph B12.10): (a)
displacement
ductility,
as
defined
in
d 1 = 0.05 0.444 d
. . . B12.8(1)
Structural steel piers The equivalent viscous damping ratio of structural steel piers is related to the displacement ductility (), as given in the following equation:
(c)
d = pier
Reinforced concrete piers The equivalent viscous damping ratio of reinforced concrete piers is related to the pier displacement ductility (d ), as given in the following equation:
(b)
(where
d 1 = 0.02 0.577 d
. . . B12.8(2)
Foundation rotation effect In lieu of more accurate determination, calculate the equivalent viscous damping ratio associated with rotation of spread footings on dense or medium dense sand or alluvium using the following equations: for dense sand and alluvium:
0.365 0.115log10
. . . B12.8(3)
for medium-dense sand:
0.52 0.17 log10
. . . B12.8(4)
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where
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= foundation rotation, in radians
(d)
Superstructure transverse flexural deformation When a superstructure is subjected to horizontal deformation involving abutment reactions without significant abutment displacement, the superstructure damping ratio may be taken as = 0.05 for a reinforced concrete superstructure, = 0.03 for a prestressed concrete superstructure, and = 0.02 for a structural steel superstructure.
(e)
Abutment deformation The equivalent viscous damping ratio associated with soil deformation at an abutment will depend on the abutment soil material and shear strain. Where the abutment is supported by piles, behaviour is further complicated. In lieu of a more accurate determination, a lower bound value of = 0.12 may be adopted for analysis.
(f)
Bearings:
(i)
Elastomeric bearings In lieu of specific manufacturers data, a value of = 0.05 may be adopted.
(ii)
Friction slider bearings In lieu of specific manufacturer’s data, the following equation may be used to calculate the equivalent bearing structural damping: d 1 = 0.05 0.67 d
. . . B12.8(5)
(iii) Elastomeric bearing in conjunction with lead plug Manufacturer’s data has to be used.
(g)
(iv)
Steel damping elements Equation B12.8(2) has to be used.
(v)
Friction pendulum bearings Manufacturer’s data has to be used.
Pile foundations where hinges develop in piles The following equation may be used:
(h)
d 1 = 0.10 0.565 d
. . . B12.8(6)
Pile/column designs In lieu of detailed studies, the following values may be used:
(i)
(ii)
Column fixed to superstructure:
(A)
Sand:
0.075 0.03 d 1 0.135
. . . B12.8(7)
(B)
Clay:
0.12 0.03 d 1 0.18
. . . B12.8(8)
Column pinned to superstructure:
(A)
Sand:
0.10 0.04 d 1 0.18
. . . B12.8(9)
(B)
Clay:
0.15 0.04 d 1 0.23
. . . B12.8(10)
(i)
Friction slabs A value of = 0.25 may be used, independent of displacement level.
(j)
Segmental piers connected by unbonded post-tensioning = 0.05.
(k)
Segmental piers connected by bonded post-tensioning = 0.05, provided tendon strain does not exceed the limit of proportionality.
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B12.9 Distribution of design horizontal force
The horizontal design force (FF) given by Equation B12.2 has to be distributed to the n bridge frame mass locations mi using the following equation: Fi
= FF
mi i
. . . B12.9
n
m i 1
i
i
where
i
= horizontal displacement demand of bridge pier or abutment i
mi
= one of the n individual masses representing the bridge frame, determined in accordance with Paragraph B2.2
B12.10 Pier displacement ductility
The displacement ductility (d) depends only on the relative values of the structural components of yield displacement and ductile displacement, as defined in the following equation:
d
= d y
d
= ductile displacement of pier excluding the foundation and bearing displacements (i.e. structural component only)
y
= yield displacement of pier excluding the foundation and bearing displacements (i.e. structural component only)
. . . B12.10
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where
B13 VERTICAL EARTHQUAKE RESPONSE
Vertical seismic response actions have to be determined from the seismic displacement demand defined in Paragraph B9.3. B14 P-Δ EFFECTS
Moments resulting from the weight supported by a pier acting through the maximum pier response displacements (P-Δ moments) have to be calculated for bridges in BEDC-3 and BEDC-4. P-Δ moments have to not exceed 30% of the pier-base moment capacity calculated in accordance with Paragraph B15. For concrete piers, the earthquake design moment has to be increased by 50% of the calculated P -Δ moment when the P-Δ moment exceeds 10% of the pier-base moment demand for the relevant earthquake load case combination. For steel piers, the earthquake design moment has to be increased by 100% of the calculated P-Δ moment when the P-Δ moment exceeds 5% of the pier-base moment demand for the relevant earthquake load case combination.
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B15 REQUIRED STRENGTH OF BRIDGE MEMBERS B15.1 Required moment capacity B15.1.1 At potential plastic hinge locations
The moment capacity at plastic hinge locations has to be determined using the expected pier material strengths in accordance with Table B15.2 Column 2 rather than the characteristic values. Flexural strength reduction factors need not be used for determination of the plastic hinge moment capacity. Moment capacity has to be not less than the moment calculated from static or dynamic analysis, including the P-Δ effects in accordance with Paragraph B14. Earthquake moment demands resulting from horizontal and vertical response need not be combined when comparing with earthquake moment capacity. Earthquake moment demands in ductile members need not be combined with gravity moment demands when determining required moment capacity of plastic hinges.
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B15.1.2 At other locations
At locations other than potential plastic hinges, moments resulting from earthquake actions, including vertical accelerations where required by Paragraph B4, have to be combined with moments resulting from permanent loads in accordance with AS 5100.2. Capacity reduction factors in accordance with the relevant material design codes have to be used. Characteristic material strengths have to be used in the design of non-hinging zones except that a value of 1.3 f c has to be used for concrete piers, where f c is the characteristic 28 day compressive strength of concrete. Formation of unintended plastic hinges are to be avoided by capacity design in accordance with Paragraph B15.3. B15.2 Material properties for seismic design
In lieu of suitable test data of material strengths, use the values specified in Table B15.2 for seismic design. Expected strengths for design of plastic hinge regions have to be based on data in Table B15.2 Column 2; material strengths for determining maximum feasible (overstrength) moment capacity of plastic hinges have to be based on Table B15.2 Column 3; and material strengths of non-hinging regions and capacity-protected actions in plastic hinges have to be based on Table B15.2 Column 4. TABLE B15.2 MATERIAL STRENGTHS TO BE USED IN SEISMIC DESIGN 1
2
3
4
Material
Expected material strength for plastic hinge zone design level
Maximum feasible material strength for plastic hinge zone capacity evaluation
Material strength for non-hinging zones
Concrete (compression)
f ce 1.3 f c
f c 1.7 f c
1.3 f c
Flexural reinforcement
f sye 1.1 f sy
f sy 1.3 f sy
f sy
Transverse reinforcement
f sy.te f sy.t
f sy.t f sy.t
f sy.t
Structural steel
f sye 1.1 f sy
f y 1.3 fsy
f sy
LEGEND: f c = f sy = f sy.t =
characteristic 28 day compressive strength of concrete characteristic yield strength of longitudinal reinforcement or structural steel characteristic yield strength of transverse reinforcement steel
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B15.3 Capacity design
Shear failure and the formation of unintended plastic hinges are to be avoided by ensuring that the strength of such locations exceeds the value of the action corresponding to the development of maximum flexural strength in the intended plastic hinges. The design shear force of the column may be determined from equilibrium of the maximum feasible flexural (overstrength) capacity of the section at the plastic hinge, calculated using upper-bound (maximum feasible) material strengths in accordance with Table B15.2 Column 3. Alternatively, the design shear force may be calculated from equilibrium at 1.4 times the design flexural strength calculated using the expected material strengths in accordance with Table B15.2 Column 2. The shear strength has to be based on the characteristic material strengths of the pier except that a value of 1.3 f c has to be used for concrete piers, together with appropriate strength reduction factors. B16 DESIGN ABUTMENT FORCES
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Determine design abutment reactions by one of the following approaches: (a)
Where Paragraph B11 provides an exemption from ductile earthquake design, determine the abutment forces by elastic modal analysis, or by multiplying the design abutment reaction from a single-mode analysis by 1.5.
(b)
Where Paragraph B11 does not provide an exemption from ductile earthquake design, determine the abutment forces by one of the following procedures: (i)
Forces determined by effective modal superposition under the design seismicity, where the stiffness of ductile elements is the secant (effective) stiffness at seismic displacement response, and the global damping used in the analysis is the system damping determined in the displacement-based design.
(ii)
Inelastic time-history analysis under the design seismicity.
B17 STRUCTURAL EFFECTS
DETAILING
REQUIREMENTS
FOR
EARTHQUAKE
B17.1 General
Care has to be taken to ensure that detailing practices recognize the potential for ductile response even when the bridge is designed to respond elastically to the design earthquake, as a consequence of the possibility of the bridge being subject to excitation exceeding the design level. Particular attention has to be given to the prevention of dislodgement of the superstructure from its support system (see Paragraph B17.2). Particular attention has to be given to the provision of viable, continuous and direct load paths from the level of the bridge deck to the foundation system. Potential plastic hinge locations in columns have to take into account the consequence of the possibility of the bridge being subject to excitation exceeding the design level. B17.2 Deck joints and bearings
Deck joints are not required to accommodate the horizontal movements due to the design seismic action. The detailing of deck joints expected to be damaged due to the design seismic action has to allow for a predictable mode of damage and an anticipated method of repair. The consequent distribution and magnitude of earthquake forces in the bridge have to be fully evaluated and considered in the design of all structural elements.
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Fixed bearings have to be designed for earthquake actions. Where these actions are outside the range of conventional bearings other measures have to be provided to prevent dislodgment of the superstructure from the support structure. Restraining devices, and connections in bridges expected to behave in a ductile manner have to be designed to withstand the horizontal design earthquake forces calculated at material overstrength (maximum feasible material strengths), but not less than the minimum lateral restraint force specified in Clause 10. The influence of such measures on the distribution and magnitude of earthquake forces in the bridge have to be fully evaluated and considered in the design of all structural elements. Vertical restraint devices have to be provided at all supports where the vertical design earthquake force opposes and is greater than 50% of the static reaction under permanent effects. The vertical restraint device has to be designed to resist an uplift force of not less than 10% of the vertical reaction at the support due to permanent effects. Vertical design earthquake forces (when applicable) have to be considered in the design of horizontal restraints that rely on any component of friction. An upper-bound estimate of the coefficient of friction has to be assumed for determination of the maximum feasible force transmitted by friction through material interfaces, when assessing demand on structural elements, such as piers, for capacity-demand conditions in accordance with Paragraph B15. Movement bearings are not required to accommodate the horizontal movements due to the design seismic action. The detailing of bearings expected to be damaged due to the design seismic action has to allow for a predictable mode of damage and an anticipated method of repair. The consequent distribution and magnitude of earthquake forces in the bridge have to be fully evaluated and considered in the design of all structural elements. At expansion ends of the superstructure (including movement joints at an abutment, pier or internal hinge) the superstructure has to overlap the substructure by a sufficient distance to prevent loss of support to the superstructure due to the design seismic action. Sufficient overlap length (see Figure B17.2) has to be provided to accommodate the relative longitudinal seismic displacement. The minimum overlap length ( Lbs), measured normal to the face of an abutment or pier (Lbs), has to be in accordance with the following equation:
Lbs
= ∆(1.5) + 0.0004Ld + 0.007 hd + 0.005 B 0.3 m
. . . B17.2
where ∆(1.5) = corner-period elastic seismic displacement demand, in metres
Ld
= length of the superstructure to the next expansion joint, in metres
hd
= average height of piers supporting the superstructure length Ld, in metres
B
= length of the seating transverse to bridge axis, in metres
L bs
L bs L bs A but m e nt
L bs Pi er
Inter nal hin g e
FIGURE B17.2 OVERLAP LENGTH L bs
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B17.3 Pile to pile cap ductile connections
For bridge structures of BEDC levels 2, 3 or 4, the connection between each pile and its pile cap has to be designed to resist tensile force levels predicted by the analysis, amplified by capacity effects (see Paragraph B15.3) but not less than 10% of the pile ultimate axial compression force N*. B17.4 Ductile welded connections
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Where the bridge is designed for reduced forces associated with ductile action, welded connections have to be designed in accordance with capacity design principles. In lieu of a more detailed assessment of the over-strength capacity of ductile steel members, a factor of 1.4 may be used for the design of welded connections. That is, welded connections have to be capable of resisting force levels corresponding to 1.4 times the yield strength of the ductile steel elements of the connection.
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APPENDIX C
SM1600 AND 300LA LOAD EFFECTS FOR SIMPLY SUPPORTED SPANS (Informative)
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This Appendix lists the bending moments and shear forces (Tables C1 and C2) from SM1600 and 300LA loadings for simply supported spans of 1 to 100 m.
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TABLE C1 SM1600 LOADING FOR SIMPLY SUPPORTED SPANS 1—100 m BENDING MOMENTS (M) AND SHEAR (V) UNFACTORED WITH NO DLA M1600 Span m
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1 2 3 4 5
(see Note) (see Note) (see Note) (see Note) (see Note) 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50
S1600
M
V
M
V
kNm 30 65 125 220 320
kN 125 170 220 260 285
kNm 25 50 105 190 275
kN 90 135 175 215 240
415 515 620 720 845 1005 1195 1390 1585 1785 1985 2190 2395 2610 2860 3160 3460 3765 4070 4375 4685 4995 5305 5635 5990 6390 6795 7200 7605 8015 8425 8835 9245 9660 10080 10495 10915 11340 11760 12185 12610 13040 13470 13900 14335
305 330 360 395 435 465 495 515 535 555 580 605 635 665 685 710 730 755 780 810 835 865 890 915 940 960 985 1005 1020 1040 1055 1075 1090 1105 1120 1130 1145 1160 1170 1180 1195 1205 1215 1225 1235
370 465 570 685 810 970 1155 1350 1550 1755 1965 2180 2405 2640 2905 3210 3520 3830 4155 4480 4815 5150 5495 5860 6245 6665 7090 7520 7960 8405 8855 9310 9775 10245 10720 11200 11690 12180 12680 13185 13700 14215 14740 15270 15805
260 290 320 355 390 420 450 475 500 520 545 575 605 630 655 685 710 735 760 790 820 845 875 900 925 950 975 1000 1020 1045 1065 1085 1105 1125 1145 1165 1185 1200 1220 1240 1255 1275 1290 1305 1325
Span m
51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100
M1600
S1600
M
V
M
V
kNm 14765 15200 15640 16080 16520
kN 1245 1255 1265 1275 1285
kNm 16345 16895 17450 18010 18575
kN 1340 1355 1375 1390 1405
16960 17405 17850 18295 18745 19195 19645 20095 20550 21005 21465 21925 22385 22845 23310 23775 24240 24710 25180 25650 26120 26595 27070 27550 28025 28505 28990 29470 29955 30440 30930 31420 31910 32400 32895 33390 33890 34385 34885 35385 35890 36395 36900 37405 37915
1290 1300 1310 1315 1325 1335 1340 1350 1355 1365 1370 1375 1385 1390 1395 1405 1410 1415 1425 1430 1435 1445 1450 1455 1460 1465 1470 1480 1485 1490 1495 1500 1505 1510 1515 1520 1525 1530 1535 1540 1545 1550 1555 1560 1565
19145 19725 20310 20900 21495 22100 22705 23320 23940 24565 25200 25840 26485 27135 27790 28450 29120 29795 30475 31160 31855 32555 33255 33970 34685 35405 36135 36870 37610 38355 39110 39870 40635 41405 42180 42965 43750 44545 45345 46155 46965 47785 48610 49440 50280
1420 1435 1455 1470 1485 1500 1515 1530 1545 1560 1575 1590 1605 1615 1630 1645 1660 1675 1690 1705 1720 1730 1745 1760 1775 1790 1800 1815 1830 1840 1855 1870 1885 1895 1910 1925 1935 1950 1965 1975 1990 2005 2015 2030 2045
NOTE: M1600 triaxle loading will govern for very short spans when DLA is included.
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TABLE C2 300LA LOADING FOR SIMPLY SUPPORTED SPANS 1—100 m BENDING MOMENTS (M) AND SHEAR FORCE (V) UNFACTORED WITH NO DLA Span m
M kNm
V kN
Span m
M kNm
V kN
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50
90 180 300 480 705 975 1275 1625 2010 2400 2790 3180 3570 3960 4350 4740 5130 5520 5910 6300 6750 7255 7860 8470 9145 9815 10490 11165 11840 12515 13190 13870 14630 15620 16610 17600 18585 19575 20565 21555 22545 23535 24525 25515 26525 27595 28795 30005 31275 32560
360 435 510 605 665 755 830 925 995 1050 1095 1135 1170 1195 1240 1285 1340 1400 1465 1515 1575 1630 1680 1725 1765 1805 1850 1895 1945 2005 2060 2120 2175 2230 2275 2325 2370 2410 2455 2505 2555 2610 2665 2720 2775 2825 2875 2925 2970 3015
51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100
33840 35125 36405 37690 38970 40255 41635 43225 44815 46405 47995 49580 51170 52760 54350 55940 57530 59120 60720 62385 64175 65990 67855 69740 71625 73510 75395 77280 79165 81050 83035 85225 87415 89605 91795 93985 96175 98365 100555 102745 104935 107125 109320 111585 113965 116380 118840 121330 123815 126300
3060 3110 3160 3215 3265 3320 3375 3425 3475 3525 3570 3615 3665 3710 3760 3815 3870 3920 3975 4025 4075 4125 4170 4215 4265 4325 4375 4425 4480 4535 4585 4635 4685 4735 4780 4830 4875 4925 4975 5030 5080 5135 5185 5235 5285 5335 5385 5430 5480 5525
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APPENDIX D
SUMMARY OF LOAD FACTORS AND COMBINATIONS (Informative) This Appendix collates load factors and load combinations presented in this Standard. Table D1 collates load factors. Load factors for construction forces and effects (Clause 22) are not included. Table D2 collates values of the dynamic load allowance.
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Table D3 collates load combinations. Load combinations for the following cases are not included in the Table: (a)
Fatigue limit state.
(b)
Construction forces and effects (Clause 22).
(c)
Permanent effects plus prestress effects at transfer (Clause 19.2).
(d)
Alternative load path design of superstructures with one or more piers or columns removed (Clause 11.1). TABLE D1 LOAD FACTORS Loading
Dead load of structure that reduces safety
Dead load of structure that increases safety
Superimposed dead load that reduces safety
Superimposed dead load that increases safety
Limit state Ultimate
Serviceability
Steel
1.10
1.0
Concrete
1.20
1.0
Concrete at transfer of prestress
1.15
N/A
Timber
1.25
1.0
Steel
0.90
1.0
Concrete
0.85
1.0
Concrete at transfer of prestress
0.90
N/A
Timber
0.80
1.0
Permanent
2.0
1.3
Removable
2.0
1.3
Special case permanent
1.4
1.0
Special case removable
1.4
1.0
Permanent
0.7
1.3
Removable
0.0
1.3
Special case permanent
0.8
1.0
Special case removable
0.0
1.0 ( continued )
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TABLE D1 (continued) Loading
Ultimate
Serviceability
Controlled fill with regular testing of soil density
1.25
1.0
All other fills and in situ soils
1.5
1.2
Groundwater
1.0
1.0
Controlled fill with regular testing of soil density
0.85
1.0
All other fills and in situ soils
0.7
1.2
Groundwater
1.0
1.0
Rail ballast and track load that reduces safety
Ballast and track
1.7
1.3
Transom track
1.4
1.2
Rail ballast and track load that increases safety
Ballast and track
0.7
1.3
Transom track
0.9
1.2
W80 wheel
1.8
1.0
A160 axle
1.8
1.0
M1600
1.8
1.0
M1600 tri-axle group
1.8
1.0
S1600
1.8
1.0
Heavy load platform (HLP)
1.5
1.0
Half of SM1600 traffic load in unobstructed lanes when applied in conjunction with HLP loading
1.8
1.0
Centrifugal force from road traffic (HLP factors shall be determined by the relevant authority)
1.8
1.0
Braking force from road traffic (HLP factors shall be determined by the relevant authority)
1.8
1.0
Pedestrian cyclist path and maintenance traffic loads
1.5
1.0
300LA rail traffic load
1.6
1.0
Centrifugal force from rail traffic
1.6
1.0
Nosing and kerb forces from rail traffic
1.6
1.0
Longitudinal braking and traction forces from rail traffic
1.6
1.0
Minimum restraint load
1.0
N/A
Collision load from road traffic
1.0
N/A
Loads on protection beams
1.0
N/A
Collision loads from rail traffic
1.0
N/A
Derailment load case A
1.2
N/A
Derailment load case B
1.0
N/A
Derailment load on kerbs
1.0
N/A
Road traffic barrier loads
1.0
N/A
Road traffic barrier connection loads
1.05
N/A
Road traffic barrier loads transmitted to bridge deck
1.1
N/A
Pedestrian and cyclist path barrier load
1.8
1.0
Soil and groundwater load that reduces safety
Soil and groundwater load that increases safety
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Limit state
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AS 5100.2:2017
TABLE D1 (continued) Loading
Limit state Ultimate
Earth pressure from traffic loads
Refer to AS 5100.3
Earthquake forces (for appropriate ARI)
1.0
1.0
Water flow (for appropriate ARI)
1.3
1.0
Wind loads (for appropriate ARI)
1.0
1.0
Thermal
1.25
1.0
Shrinkage and creep
1.2
1.0
Prestress secondary effects
1.0
1.0
Prestress effects at transfer
1.15
1.0
Differential settlement effects
1.5
1.0
Accurate records and information are available
1.5
1.0
Other sites
2.0
1.0
1.3
1.0
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Serviceability
Loading
Fatigue limit state
A160 axle (determined from 70% of the load)
1.0
M1600 (determined from 70% of the load without UDL)
1.0
300LA rail traffic
1.0
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AS 5100.2:2017
124
TABLE D2 DYNAMIC LOAD ALLOWANCE Dynamic load allowance ( )
Loading Road traffic loads (see Note 1)
W80 wheel
0.4
A160 axle
0.4
M1600 tri-axle group (see Note 2)
0.35
M1600 (see Note 2)
0.3
S1600 (see Note 2)
0.0
Heavy load platform load (HLP) (see Note 3)
0.1
Centrifugal force, braking force or pedestrian load
0.0
Fatigue load
A160 axle
0.4
M1600 without UDL
0.3
M1600 tri-axle group without UDL
0.35
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Pedestrian, cyclist path and maintenance traffic loads
0.0
Rail traffic loads (see Note 4)
Bending effects—ballasted deck spans, open deck spans or spans with direct rail fixation (see Notes 5, 6)
2.16 0.2 0.27 0.67 0 . 5 Lα 0.20
Bending effects—transoms for open deck bridges and local effects for direct fixed tracks (see Note 6) Shear, torsion and reaction effects
1.0 0.67 of the value for bending effects, or 0.0 if the DLA leads to greater safety or stability
Centrifugal, braking and traction force
0.0
Nosing load
0.0
Deflection Fatigue load
0.67 of the design DLA Half of the design DLA (see Note 7)
Derailment loads
0.0
NOTES: 1
For application of DLA below ground level, see Clause 7.7.3.
2
Including the UDL component of the traffic load.
3
Heavy load platform travels at a maximum speed of 10 km/h. A higher DLA ( ) may apply where this speed is exceeding.
4
For application of DLA below ground level, see Clause 9.5.4.
5
The value of for steam locomotives to be increased by 20%.
6
Where a transition approach to a bridge abutment is not provided, then α to be increased by not less than 50% of the calculated dynamic load allowance unless otherwise approved by the relevant authority.
7
For multiple track bridges the dynamic load allowance for the fatigue load is 0.0.
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TABLE D3 ULS LOAD COMBINATIONS (see Note 1) Load factors A Minimum strength and stability
B Road/rail traffic
C Pedestrian cyclist path maintenance traffic
D Minimum restraint
E Collision
F Road traffic barrier
G Earth pressure from traffic
H Earthquake
I Water flow
J Wind
K Thermal
Steel
1.35
1.1
1.1
1.1
1.1
1.1
1.1
1.1
1.1
1.1
1.1
Concrete (see Notes 2, 3)
1.35
1.2
1.2
1.2
1.2
1.2
1.2
1.2
1.2
1.2
1.2
Timber
1.35
1.25
1.25
1.25
1.25
1.25
1.25
1.25
1.25
1.25
1.25
Clause 6.2 Dead load that increases safety
Steel
0.9
0.9
0.9
0.9
0.9
0.9
0.9
0.9
0.9
0.9
0.9
Concrete (see Note 3)
0.9
0.85
0.85
0.85
0.85
0.85
0.85
0.85
0.85
0.85
0.85
Timber
0.9
0.8
0.8
0.8
0.8
0.8
0.8
0.8
0.8
0.8
0.8
Clause 6.3 Superimposed dead load that reduces safety
Permanent
1.35
2.0
2.0
2.0
2.0
2.0
2.0
2.0
2.0
2.0
2.0
Removable
1.35
2.0
2.0
2.0
2.0
2.0
2.0
2.0
2.0
2.0
2.0
Special case permanent
1.35
1.4
1.4
1.4
1.4
1.4
1.4
1.4
1.4
1.4
1.4
Special case removable
1.35
1.4
1.4
1.4
1.4
1.4
1.4
1.4
1.4
1.4
1.4
Permanent
0.9
0.7
0.7
0.7
0.7
0.7
0.7
0.7
0.7
0.7
0.7
Removable
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
Special case permanent
0.9
0.8
0.8
0.8
0.8
0.8
0.8
0.8
0.8
0.8
0.8
Special case removable
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
Load effects—Permanent effects
Clause 6.2 Dead load that reduces safety
125
Clause 6.3 Superimposed dead load that increases safety
( continued )
AS 5100.2:2017
Standards Australia
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AS 5100.2:2017
Standards Australia
TABLE D3 (continued) Load factors B Road/rail traffic
C Pedestrian cyclist path maintenance traffic
D Minimum restraint
E Collision
F Road traffic barrier
G Earth pressure from traffic
H Earthquake
I Water flow
J Wind
K Thermal
Controlled fill with regular testing of soil density
1.35
1.25
1.25
1.25
1.25
1.25
1.25
1.25
1.25
1.25
1.25
All other fills an in situ soils
1.35
1.5
1.5
1.5
1.5
1.5
1.5
1.5
1.5
1.5
1.5
Groundwater
1.0
1.0
1.0
1.0
1.0
1.0
1.0
1.0
1.0
1.0
1.0
Controlled fill with regular testing of soil density
0.9
0.85
0.85
0.85
0.85
0.85
0.85
0.85
0.85
0.85
0.85
All other fills an in situ soils
0.9
0.7
0.7
0.7
0.7
0.7
0.7
0.7
0.7
0.7
0.7
Groundwater
1.0
1.0
1.0
1.0
1.0
1.0
1.0
1.0
1.0
1.0
1.0
Clause 6.5 Rail ballast and track load that reduces safety
Ballast and track
1.35
1.7
1.7
1.7
1.7
1.7
1.7
1.7
1.7
1.7
1.7
Transom track
1.35
1.4
1.4
1.4
1.4
1.4
1.4
1.4
1.4
1.4
1.4
Clause 6.5 Rail ballast and track load that increases safety
Ballast and track
0.9
0.7
0.7
0.7
0.7
0.7
0.7
0.7
0.7
0.7
0.7
Transom track
0.9
0.9
0.9
0.9
0.9
0.9
0.9
0.9
0.9
0.9
0.9
Clause 16 Water flow loads and buoyancy at mean water level
1.3
1.3
1.3
1.3
1.3
1.3
1.3
N/A (see Note 7)
1.3
1.3
Clause 19.1 Shrinkage and creep effects (zero effects and full effects)
1.2
1.2
1.2
1.2
1.2
1.2
1.2
1.2
1.2
1.2
Clause 6.4 Soil and groundwater loads that reduce safety Clause 6.4 Soil and groundwater loads that increase safety
126
A Minimum strength and stability
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TABLE D3 (continued) Load factors A Minimum strength and stability
C Pedestrian cyclist path maintenance traffic
D Minimum restraint
E Collision
F Road traffic barrier
G Earth pressure from traffic
H Earthquake
I Water flow
J Wind
K Thermal
Clause 19.2 Prestress effects (before and after losses) (see Note 3)
1.0
1.0
1.0
1.0
1.0
1.0
1.0
1.0
1.0
1.0
Clause 20.1 Differential settlement effects
1.5
1.5
1.5
1.5
1.5
1.5
1.5
1.5
1.5
1.5
Clause 20.2 Mining subsidence effects
Accurate records and information available
1.5
1.5
1.5
1.5
1.5
1.5
1.5
1.5
1.5
1.5
Other sites
2.0
2.0
2.0
2.0
2.0
2.0
2.0
2.0
2.0
2.0
1.3
1.3
1.3
1.3
1.3
1.3
1.3
1.3
1.3
1.3
Clause 21 Forces from bearings
127
B Road/rail traffic
Load effect—Thermal effects
Clause 18.2 Variation in average bridge temperature
0 and 1.0
0 and 1.0
1.25
Clause 18.3 Differential temperature
0 and 1.0
0 and 1.0
1.25
Load effect—Transient loads
Clause 7 Road traffic including dynamic effects
1.8
Half of SM1600 applied in conjunction with the heavy load platform
1.8
Heavy load platform
1.5
Centrifugal force and braking (see Note 4)
1.8
0 and 1.0
0 and 1.0
0 and 1.0
( continued )
AS 5100.2:2017
Standards Australia
SM1600
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Standards Australia
TABLE D3 (continued) Load factors A Minimum strength and stability
Clause 9 Rail traffic including dynamic effects
300LA
1.6
Centrifugal force and nosing and kerb forces
1.6
Longitudinal braking and traction forces
1.6
Clause 10 Minimum restraint load
1.5 (see Note 6)
C Pedestrian cyclist path maintenance traffic
D Minimum restraint
E Collision
F Road traffic barrier
0 and 1.0
1.5
G Earth pressure from traffic
H Earthquake
I Water flow
0 and 1.0
J Wind
K Thermal
0 and 1.0
0 and 1.0 128
Clause 8 Pedestrian, cyclist path and maintenance traffic loads
Clause 11 Collision loads
B Road/rail traffic
1.0
Except for rail derailment load case A
1.0
Rail derailment load case A
1.2
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Clause 12.2 Road traffic barrier loads
1.0
Clause 12.2 Road traffic barrier anchorage loads
1.05
Clause 12.3 Road traffic barrier loads transmitted to bridge deck cantilevers
1.1
Clause 12.5 Pedestrian and cyclist path barrier load
1.8 ( continued )
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TABLE D3 (continued) Load factors A Minimum strength and stability
B Road/rail traffic
C Pedestrian cyclist path maintenance traffic
D Minimum restraint
E Collision
Clause 14 Earth pressure from traffic loads
F Road traffic barrier
G Earth pressure from traffic
H Earthquake
J Wind
K Thermal
Refer to AS 5100.3
Clause 15 Earthquake loads
1.0
Clause 16 Water flow forces Clause 17 Wind loads
I Water flow
1.3 1.0 (see Note 8) For load combinations for fire effects, refer to specialist literature
129
Clause 26 Fire effects
1.0
NOTES: 1
Load combinations for the following cases are not included in the Table— (a) fatigue limit state; (b) construction forces and effects (Clause 22); (c) permanent effects plus prestress effects at transfer (Clause 19.2); and (d) alternative load path design of superstructures with one or more piers or columns removed (Clause 11.1).
2
For precast construction, where appropriate control and monitoring are exercised over dimensions, the authority may allow a reduction of load factor to not less than 1.1 for ultimate limits states for the cases where the dead load reduces safety. See Clause 19.2 for the load combination at transfer of prestress. Centrifugal and braking forces due to road traffic to not be applied simultaneously.
5
Centrifugal and nosing forces due to rail traffic to not be applied simultaneously.
6
Road and rail bridges with access or maintenance walkways not intended for public use are not required to be designed for the simultaneous occurrence of the road and rail live load and the walkway live load.
7
The permanent loads due to ‘Water flow loads and buoyancy at mean water level’ are not applicable to load combination (I) ‘water flow’. The transient loads due to ‘Water flow forces’ loads shall be used instead.
8
For load combination (B) the wind load is to be included using a design wind speed of 35 m/s in all locations.
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AS 5100.2:2017
130
BIBLIOGRAPHY Structural design actions Part 0: General principles
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AS/NZS 1170 1170.0
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NOTES
AS 5100.2:2017
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AS 5100.2:2017 132
NOTES
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